Can't fullscreen or change resolution unless the steam_api.dll file is moved out of the game's main folder. This expectedly also breaks achievements and makes the game not close properly so i have to force stop it in steam (and probably more I haven't encountered yet).
Deleting config.data or reinstalling also don't work. I have also tried generating a config.dat file without the dll and then adding it back and it did nothing.
edit: i found a fix for this by setting launch command to
SteamDeck=0 %command%
to make the game think its not running on a steam deck