As long as the game on steam isn’t using a DRM like Denuvo, Enigma, etc then I can backup and play them even without steam.

It’s just that if the game uses Steam DRM then I’d have to use a steam emulator like Goldberg/gbe_fork to play the game. Sometimes you’d also have to remove SteamStub DRM from the game exe files using Steamless.

GOG is easier since you don’t need to mess with steam emulators and such. You also won’t run into the issue of having to manually create windows registry entries that some old games need. GOG installers will create those windows registry entries for you.

The source code is even hosted on GitHub which is owned by Microsoft.