So the conclusion I came to yesterday after spending what must've been twelve hours straight of experimentation:
Proton is fucking trash for anything *not-Steam* and, unless newer apps can use it properly, WILL break things that otherwise should work.
And it's a bit annoying that Wine-GE isn't being updated anymore, because newer Wines are actually what e.g. fixed Gaia Attack 4's video files - but as neat as Soda or Wine-TKG are, none of them have the same FSR hack for fake resolutions.