@djlink It's never actually windowed, the games run in their own compositor, if you toggle between windowed / fullscreen in-game, nothing changes, it's always fullscreen, looks exactly the same.

But for some reason, some games treat running fullscreen differently, and that hurts performance.
No idea why, but I've seen it myself a few times, so I set them to windowed (which often is the default anyway).

I've seen that mentioned in PCGamingWiki a few times as well, so this doesn't seem to be a SteamOS/Linux specific problem :Blobhaj_Thinking: