As far as switching out Explorer goes, it’s not actually the window manager, that’s Aero since Vista - but it is the shell on desktop editions of Windows… But not all editions. Some server editions (“core”) and some specialized other ones have the shell set to literally just a cmd window. There’s no taskbar, no Start, no desktop icons, etc. There’s a cmd window that if closed triggers a reboot. Of course other things can be started from it.
I’m not sure if there’s a setting that could be changed to make a desktop edition behave like that or vice versa.