Larian's previous game (Divinity Original Sin 2) didn't have a native port, the one before that did. I think it's unlikely that BG 3 will get a native port but it seems to work well enough through Proton.
Which previous games were you looking at by the way, BG1 and BG2? BG3 has little to do with those except for the setting, it's a really different game (some dislike it for that).
I've had more luck streaming games with Moonlight (+ Sunlight server on game pc) than using Steam Link, both for controller support in certain games and just better latency. Even on Steam Deck, when I'm at home I barely notice a difference, it saves a lot of battery and I can AAA games without compromising in graphics settings.