Ah yes, window managers vs desktop environments.
You can run either KDE or GNOME and use their default window managers or you can use any other window manager that is compliant with that desktop environment.
KDE and GNOME are desktop environments.
OpenGEU is a distro that is uses the GNOME desktop environment but the
Enlightenment window manager. You can see a list of window managers
here. Some can work with KDE or GNOME and some won't integrate well even though you can still possibly run them together.
For years, I ran AfterStep or Enlightenment standalone, without any kind of desktop environment like KDE or GNOME.
Peace...