Need help with (policy based) routing

[cfios]

Just playing around with this more, if

route_allowed_ips="0"

on the Wireguard client (Mullvad) is set, I am able to connect to the wgserver. The final issue, which is really just a zero-sum, none of my traffic goes through Mullvad this way.

I have played around with https://docs.openwrt.melmac.net/vpn-policy-routing/#wireguard-tunnel

Routing Wireguard traffic may require setting net.ipv4.conf.wg0.rp_filter = 2 in /etc/sysctl.conf. Please refer to issue #41 for more details.

and followed the issue to read

net.ipv4.conf.default.rp_filter=2
net.ipv4.conf.all.rp_filter=2

The only observable change is that if I don't pass traffic to Mullvad, both Wireguard interfaces will handshake with their corresponding peer (Mullvad handshakes, still doesn't traverse the interface).

I've also found another post attempting the same thing, although it appears they have given up on this:

Simultaneous Wireguard Server and Mullvad Wireguard Client Setup?

Brilliant, thanks. So should my port-forward for this interface connect WAN to LAN or Mullvad to LAN? WAN to LAN makes sense, but only if I allow forwarding from LAN to WAN interfaces in the firewall. Mullvad to LAN makes sense because it's the predominant internet gateway, as such, but it doesn't allow 'normal' port-forwarding - should I pre-allocate a port in Mullvad and use that for the server if this is the case? Thanks again!