FWIW, Proton has handled everything I’ve tried in my Steam library except Cities: Skylines. I spent eight hours just yesterday playing Factorio at 4K on KDE.
That said, I don’t play GPU-melting games in favour of $20-$30 indie games, so YMMV. I wasn’t even aware of Proton when Windows finally gave me one too many OneDrive entreaties, and I was pleasantly surprised by the state of affairs on Linux.