Wayland requires a Desktop Environment from what I can see. There is Sway, but that is a tiling environment, but I know little about that. So for "floating windows", all there is GNOME3, KDE and Enlightenment. DE are heavy to begin with, cwm on X is very lite on resources.
This I am not sure about, but from what I have read, all window processing (rendering) needs to be done by the "Widow manager". In X you just call functions.