Currently playing Baldur’s Gate 3 and Astarion came to my mind immediately

As a guy who has a lot of experience with old emulated Nintendo games and things like that, I keep a bunch of ROMs on a cloud storage service for backup. But all those files add up and eat storage space. For a service like this, do you just have the installers themselves stored for easy installing/uninstalling? How big are those files, for storage purposes? I have a lot of PC games, but, you know, I don’t like paying for all of them. Are you able to have tons of “alternative” Steam games or does storage space run out quick?