Most stuff is fully rewritten/replaced. KDE and GNOME (maybe XFCE) are special cases. Sway acting as the Wayland version of i3wm is more what I expect. There was an early project to replicate AwesomeWM called WayCooler, but after a few years of trying to rewrite some major parts in Rust, the project died. There was a list of wlroots-based compositors at some point where most were replacements for the various old WMs.

It doesn't. Or at least it didn't last I checked, maybe that's changed, but I doubt it. I've tried the Wayland alternatives, and they left such a bad taste in my mouth that I'd really rather never touch Wayland again. Sway in particular was an exercise in frustration, the damned thing refused to use the right keyboard layout no matter how hard I tried.