Reporting back:

I tried installing The Witcher and Psychonaut. Both worked mostly seemlessly after prompting to install Wine-GE. The main issue I'm having is with controller support, but this may just be a result of trying much older games and mixing that with trying to use Steam Input through the Heroic launcher. I suspect this can be alleviated by using the "Automatically add games to Steam" option and launching the games through Steam, rather than Heroic. Alternatively, if you're willing to map your bindings for each game, or you are on something other than a Steamdeck and use keyboard and mouse, you should be fine.

I recommend giving a game you already own on Gog a try and seeing how it works for you.