This past weekend I played Green-White Midrange at Pro Tour Dominaria and went 7-3 in the Constructed rounds. The deck was primarily designed by Chris Fennell, though I and a few others helped tune it. It's a great choice for the team RPTQs this weekend since it slots nicely into the third slot. I expect most teams to show up with a red deck built around Goblin Chainwhirler (either mono-red or black-red) and a Blue Control deck. These are likely the two best decks to have in your arsenal, which means your third deck will be either Mono-Green Stompy, Black-Green Constrictor, or this Green-White deck. I believe green-white is the best choice among the Green decks for your third deck as well as a great choice by itself in Standard.
Here is the list I played to a 7-3 record at the Pro Tour.
The only change I would make is replacing the third Baffling End with a third Thopter Arrest.
If you are playing the deck in your RPTQ, likely the only duplicate card is Cast Out in your White-Blue Control deck. If you're looking to replace that card, the next best option is Ixalan's Binding. Swapping Cast Outs for Ixalan's Bindings will hurt us a little, but not in a significant way. The one play it means we will not be able to make though is Casting Out the Opponent's Cast Out on Shalai, Voice of Plenty in response to Settle the Wreckage. Since Shalai must be the target for your opponent's Cast Out, there will often be one under a Cast Out. This makes this play come up fairly often in the matchup. If instead we have Ixalan's Binding, then we can still get rid of the opposing Cast Out and free our Shalai and thereby render Settle the Wreckage uncastable, but it won't be as much of a blowout since they can use their mana to cast something else instead, such as another Cast Out or a Glimmer of Genius.
In the early turns we want to play mana accelerants. This allows us to ramp into our four-, five- and six-drops. Casting a third-turn boat ( Skysovereign, Consul Flagship) is often game over for the opponent no matter what they are playing. Similarly, casting a third turn Shalai, Voice of Plenty with Blossoming Defense open and then following it up with Lyra Dawnbringer and attacking for four points of lifelink is very hard to stop, especially for the red decks.
If the opponent spends their early turns killing our mana accelerants instead of playing their own creatures, then we are under no pressure and have time to deploy our larger threats and still take over the game. If instead they deploy threats to pressure us, then we ramp into our larger threats. So when facing a red deck, they are kind of stuck between a rock and a hard place against us. Their best plan is likely to kill our accelerants and hope we stumble on mana with a bunch of expensive cards in hand. Having Ixalan's Binding instead of Cast Out could hurt us in this regard, but I still think we have plenty of mana sources to deploy our spells in most games – 24 lands and 11 mana accelerants. That's 35 of our 60 cards that produce mana. And we really only need to get to five in most games.
I already mentioned the blowout involving Cast Out, Shalai, and Settle the Wreckage, but there is another similar blowout that comes up fairly often. If the opponent plays Glorybringer ad attacks into Shalai, they will almost always exert it to try and kill Shalai. If they exert, Shalai is the only legal target due to Shalai's ability. Whether they choose to exert or not exert, we can blow them out either way with a Blossoming Defense. If they exert, cast it in response. This counters the ability since Shalai gets hexproof from Blossoming Defense and then you can block the Dragon with your 5/6 Shalai. So you basically traded one mana and a card for their five mana and their Glorybringer. And if they do not exert, then you still just block and give Shalai +2/+2 with Blossoming Defense. The blowout is about the same as a Chandra's Defeat blowout in the red mirrors when you get to take out a Dragon with it.
Another play to keep an eye out for is Abrade on your vehicle. If you have Shalai in play, it is best to have enough power worth of creatures to crew your vehicle twice. This way if they Abrade in response to your attempt to crew, you can crew again in response so that your vehicle gains hexproof. The same principle applies when you are holding Blossoming Defense. Otherwise it dies to Abrade since it is not a creature until the crew ability resolves.
Another tip to keep in mind is against Red decks you often want to put a Rishkar counter on your Llanowar Elves to get them out of range of Goblin Chainwhirler, even though they don't benefit from the mana producing ability since they already have that. Also regarding Rishkar, if the opponent has Soul-Scar Mage on the battlefield and then casts Goblin Chainwhirler, the -1/-1 counters will Cancel out the +1/+1 counters granted by Rishkar and thereby render your creatures unable to produce mana. However, Rishkar only cares about a creature having counters, not necessarily +1/+1 counters. So if Goblin Chainwhirler or whatever else puts a -1/-1 counter on one of your creatures that doesn't already have a +1/+1 counter on it, it can then tap for mana due to Rishkar's ability since -1/-1 counters are still counters and that's all Rishkar cares about.
-4 Llanowar Elves
-1 Jadelight Ranger
-1 Rishkar, Peema Renegade
+1 Thrashing Brontodon
+2 Baffling End
+3 Thopter Arrest
We almost moved Llanowar Elves to the sideboard since we (correctly) predicted a ton of red decks. Ultimately, we decided it is better to play them main and just board them out against Goblin Chainwhirlers. For the RPTQ you will only play against Goblin Chainwhirler a third of the time on average, or less if not every team shows up with a Chainwhirler deck, so it's definitely correct to play them main for that event. They are pretty much our best card in every non-red matchup.
In game one, you usually want to cast the boat as soon as possible, often killing Soul-Scar Mage over any other creature they have. That's because our way to win often involves Lyra Dawnbringer and keeping them from being able to shrink our lifelink Angel is usually more important than taking out a creature that hits us for three like as Kari Zev or Goblin Chainwhirler. The only threats I am more likely to Cast Out than Soul-Scar Mage are Hazoret, Rekindling Phoenix or Glorybringer.
In post-board games we get a bunch more enchantment-based removal spells. Baffling Ends help handle their early pressure or their Soul-Scar Mages while Thopter Arrest can help take down their larger threats such as Phoenix, Dragon or Hazoret. Thrashing LeBrontodon James also comes in, not because they have artifacts or enchantments we want to kill but rather because the four-toughness survives all their burn spells while the three power kills all their early threats.
Overall, the matchup has proven favorable from the green-white side, though it is close. I beat it more times than I lost to it at the Pro Tour, but it did account for two of my three losses in the event. My other loss was to Kelvin Chew playing Blue-Black Control, not because the matchup is rough but instead because Kelvin Chew is unbeatable at Magic. The third Thopter Arrest in the board should help that matchup because it tends to be all about whether they can stick a Scarab God.
-3 Lyra Dawnbringer
-2 Aethersphere Harvester
-1 Skysovereign, Consul Flagship
-1 Blossoming Defense
-2 Rishkar, Peema Renegade
+1 Thrashing Brontodon
+2 Heroic Intervention
+2 Nissa, Vital Force
+3 Prowling Serpopard
This matchup has been overall favorable for me, especially in post-board games. We present all the threats in the matchup and we have tools to Thwart any of their answers to our threats, but sometimes the cards line up perfectly from their end and we lose. Sometimes we must take risks like walking into a Fumigate or Settle the Wreckage, but usually we have the ability to play around their best cards against us.
I already mentioned the play of Casting Out their Cast Out (on Shalai) to wreck their Settle the Wreckage, but there are other sequences that are similarly backbreaking blowouts. One is casting Heroic Intervention in response to Fumigate (or in response to Cast Out or Seal Away if you don't have Blossoming Defense to use instead). Another is playing Prowling Serpopard into Shalai, Voice of Plenty. The Cat Snake makes the Angel uncounterable, and then once the Angel resolves it gives the Cat Snake hexproof, which allows it to attack safely without the possibility of getting exiled by Seal Away. So even if the opponent has Essence Scatter and Seal Away in hand and enough mana up to cast either, they can do nothing with their mana on that turn.
Another cool play is forcing the opponent to Fumigate and then untapping and casting Nissa, Vital Force to keep the pressure on. Depending on what their life total is at, you may want to begin by using the Regrowth ability to bring back Shalai or whatever. Otherwise you likely just want to start hitting for five. Nissa is also great at pressuring Teferi, Hero of Dominaria.
Another trick is that if they Cast Out or Seal Away your card, you can Cast Out, Naturalize or sacrifice Thrashing Brontodon in response to the enchantment's ETB trigger. Since the enchantment is gone when the "until" ability resolves, it will never exile the permanent. This means attacking creatures are still attacking. This play often comes up when the opponent plays Teferi and untaps to lands and then tries to Seal Away one of your creatures that is attacking Teferi. A Naturalize in this case or a pre-combat cast Brontodon to take out the Seal Away can finish off a Teferi. If it's a Thrashing LeBrontodon that keeps the Seal Away or Cast Out from ever exiling the target though, you have to say in an NBA commentator's voice, "OoOoOOoH!! Blocked by James!!!"
Another thing to keep in mind for the close games that often come down to hedging is to attack with your non-vehicle creatures into Settle the Wreckage if you have more creatures to play that can crew the vehicles the following turn. This allows you to keep your Fumigate-proof threats on the battlefield. You also generally want to hold Walking Ballista in hand until after a Settle the Wreckage since that is one of our few ways to take advantage of all the excess lands granted by Settle.
Ajani also really shines in this matchup. Oftentimes the opponent is forced to tap out, either on their own turn or during combat. This will often open the door for us to resolve Ajani. They have Cast Out to get rid of Ajani temporarily (until we draw a Cast Out or Naturalize effect to get him back), but even then we already got one activation out of him, which will often give us plus-two cards. Ajani is also great against The Scarab God and Hazoret the Fervent in those matchups and is our best way to pull ahead in the green midrange mirrors. Well, Ajani and Boat and Lyra are our ways to get ahead.
Skywhaler's Shot is mostly for the green matchups as it can kill any of their threats that we care about. It's also not terrible against decks with Torrential Gearhulk if they also have Lyra Dawnbringer. Also be sure to keep Walking Ballista in the deck in post-board games against control decks. It is a way to utilize all the extra mana they give us from Settle the Wreckage while also helping to finish off planeswalkers.
This deck is a great choice for this weekend, especially given the team unified restrictions. It's a great deck that doesn't take anything away from the other two best decks in the format (Red and White-Blue Control) other than Cast Out, which can be replaced by Ixalan's Binding without much trouble. And even if you are playing in an individual Standard event, none of the top decks are bad matchups for this deck. If you're looking for a third deck for your RPTQ tournament or you just want to play something other than a Goblin Chainwhirler deck, this would be my recommendation.