From what I know, Wayland is a standalone server. It can use X.org server for server<->client stuff.
It's a library combining minimal display-related technologies (X driver, wayland protocol handler) to be used by a compositor to implement a Wayland protocol server. It appears that the compositor could implement network forwarding, although the current sample implementation does not.
Since X server can be Wayland clients, X technologies can be used beneath. The eventual goal is apps on Wayland without X, but this takes improving the Wayland protocol to a point it suits apps.
Rendering Client-side means frozen apps can't move by their top bar, but could move using the option on the window list (since Wayland holds position info). If it's a problem, GTK/Qt may implement a UI thread to keep the app UI alive. An old message queue could also produce a not-responding box.