At this point, Goblin Chainwhirler's grip on the Standard metagame is firm. How he manages to hold onto the metagame at the same time as those chains he so flippantly whirls about is another story, but the fact is that he does and it's now our job to find a deck that can compete against it.
U/W Control with Teferi has failed. Green Aggro with Ghalta, Primal Hunger or Winding Constrictor has failed. W/B Aggro with Toolcraft Exemplar definitely failed. It's time to get creative rather than rehashing the same ideas with a slightly different sideboard plan.
That's what Marcos Paulo De Jesus Freitas did at Pro Tour Dominaria, putting up an impressive 7-3 finish in the Constructed rounds with a G/W deck that defies traditional classification. You don't often find Fumigate and Merfolk Branchwalker in the same deck, but I'm not worried about traditional deckbuilding aesthetics. I just want to put these Mountain players in their place, and green and white make the color pair to do just that.
As weird as it looks, the list passes the first smell test: don't play one-toughness creatures. Merfolk Branchwalker can be one toughness, but in that case at least you got an extra card out of the deal. Same for Walking Ballista, but you can control that by simply not casting it for two mana into a potential Chainwhirler. You can see more about proper Ballista tactics in this great breakdown from the Golgari Queen herself, Jadine Klomparens.
The second test is to be able to contend with the high-end red threats: Hazoret the Fervent, Rekindling Phoenix, Chandra, Torch of Defiance, and Glorybringer. The white removal does just that, and Angel of Sanctions is particularly good as a removal spell that stabilizes the battlefield against smaller creatures and generates card advantage.
And the third test is whether the deck can hold its own against those who stubbornly refuse to play Goblin Chainwhirler. It might have a few maindeck bricks against control strategies, but there's plenty to bring in from the sideboard; I especially like the Fleetwheel Cruisers and Nissa, Vital Forces as threats that can immediately bring down a Teferi, Hero of Dominaria. Against other aggro and midrange decks, you're another pile of efficient removal, good creatures, and planeswalkers, so everything checks out.
How much value Marcos gained from players not expecting the maindeck sweepers is unclear, but even accounting for that, this list has a lot going for it and you must applaud the creativity.