I have civ 3 running on my tablet through an emulator, could possibly even do civ 4 but haven’t tried that yet. It takes up next to no space, the graphics are light enough you could run it on a potato and it’s one of the best civ iterations I reckon.
Steam used to allow you to convert certain physical games to digital if you put the CD key into Steam’s “Add a Non-Steam Game” menu.
It wasn’t all games but quite a few, so if you’re sitting on a big physical library this is a legitimate option.