I do not know what xfce really has to do with X11 vs Wayland, but you could - if one wanted - build an X server that integrates a compositer and window manager. I do not think this has any real technical advantage and I think a modular design is stronger from an engineering point of view.

Tear-free is more a driver issue, I also do not see any Wayland advantages here. Probably xorg does not enable it by default