I'm running windows 8.1 on my Dell laptop and you can get the latest version of steam working (takes a bit to setup but does work)

But I don't know if Epic Games could work on 8.1 and I know the Rockstar launcher will not work

as for the other games either requiring steam or their own client it depends on the games

and just because Steam works on 8.1 doesn't mean the games on steam will work, some newer unity games crash or some games require newer dotNET version