Thanks for cracking the PipeWire puzzle.
For the rest of the setup, if you need GUI apps, see Incus / LXD profile for GUI apps: Wayland, X11 and Pulseaudio In this case, the PulseAudio socket is mounted as a disk device instead of a proxy device.
Is it better to use disk devices or proxy devices? It shouldn’t make a difference as long as both are reliable.