If you look at any modern desktop application, e.g. those built over GTK or QT, then they're basically rendering stuff into a pixmap and pushing it over the wire. All of the drawing primitives made X11 efficient once upon a time are useless, obsolete junk, completely inadequate for a modern experience. Instead, X11 is pushing big fat pixmaps around and it is not efficient at all.

So I doubt it makes any difference to bandwidth except in a positive sense. I bet if you ran a Wayland desktop over RDP it would be more efficient than X11 forwarding. Not familiar with waypipe but it seems more like a proxy between a server and a client so it's probably more dependent on the client's use/abuse of calls to the server than RDP is when implemented by a server.

What kind of bugs are you running into? The original Waypipe proposal claimed that it was pushing less data than X. Let’s hope it gets faster in the future.