SteamOS is very different from Arch. There’s almost too much to list here. But it uses an image based read only OS, a fully custom wayland desktop environment/c

SteamOS is very different from Arch. There’s almost too much to list here. But it uses an image based read only OS, a fully custom wayland desktop environment/compositor, does not have pakman, software is distributed either through steam or flatpak, OS image updates have their own mechanism. And a whole lot of preinstalled drivers and software for things like controller support which typically don’t come out of the box on Linux distros. The whole OS is made for controllers, no need for a mouse/kb for anything.