I don't know about PD, but I found that native clients will accept RAs over WireGuard just fine. I only have a /64 at the moment unfortunately, so I can't really use this mechanism at the moment, but I did set up a ULA by giving radvd the following config:

    interface wg-server
    {
        AdvDefaultLifetime 0;
        AdvSendAdvert on;
        prefix fdf4:a694:0e43:c0de::/64 {
            AdvOnLink on;
            AdvAutonomous on;
        };
    };
    

I use the equivalent of fdf4:a694:0e43::/48 across all interfaces to make the ULA routable without too much effort.

I don't see why you wouldn't be able to set up a normal IPv6 SLAAC config, assuming you have the address space to advertise a full /64 on the interface.