I’m not familiar with qtile, but I’m fairly sure there’s currently no way to get information about the active window on mutter unfortunately.
Thing with wayland is, each compositor has to implement things their own way, so you’re limited to what your compositor allows you to do.
For instance, you can get window information in sway with swaymsg. On other compositors you may have to find workarounds.
There is Nyrna, but it doesn’t work on Wayland.
Afaik saving to swap isn’t possible as it’s something managed by the kernel, although you can try tweaking cgroups. Nyrna also mentions that this isn’t currently possible.