Outside of a handful of multiplayer games pretty much any game will work under proton, new or old. Stalker 2 worked out the box on release day, early awkward 3D games like Gothic runs just fine, and your early point and click games will likely run just fine. Out of my 460 games*, only EA WRC doesn't work because they introduced kernel level anti cheat after release.

*Edit: Just to clarify i haven't tested all my games, but I have played a good number of them. Also another game that doesn't run is Ground Control 2, but that doesn't work on Windows since about 7 or 10, so it doesn't count! ^^