I tried Lutris and Bottles, but I didn't give Heroic much of a shot. Personally, I think Bottles is the nicest one, though I'm still using Lutris. Although, for my use case (Japanese language visual novels), Lutris makes it easier to select Japanese Locale for specific games, and hopefully with the next release, it will let you choose Locale when installing games: https://github.com/lutris/lutris/issues/493

I think the Lutris Installer is generally less finicky than Heroic and Bottles as it automatically detects the game executable after installation. It isn't always successful, but it usually is.

Does the Heroic Flatpak bundle a runtime similar to the Lutris Runtime? It seems to imply that it bundles Wine versions, but what about all the other usual dependencies, like DXVK, Faudio, etc.? There doesn't seem to be much information on that.

I'll share the one thing that made my life much easier: Gamescope. So many visual novels don't fullscreen properly, and Gamescope is a great workaround for that. The upscaling stuff is nice too.