At the moment, I have a very simple firewall rule for my router to ensure traffic between private and guest networks don't ever interfere. The configuration for that is here. Additionally, I have a helper function of sorts to create wireguard interfaces. Given I'm very new to firewall rules and routing, I'm not sure how to ensure that all traffic from the private network is routed via the wireguard interface but the guest network's traffic exits without ever touching the wireguard interface. Let's call it wg0 on the router.

I believe that this setup will require the following additional rules to the forward chain in the router-fw table:

iifname "isolated" oifname "wg0" drop
iifname "wg0" oifname "isolated" drop

iifname "trusted" oifname "wg0" accept
iifname "wg0" oifname "trusted" accept

iifname "wg0" oifname "wan" accept
iifname "wan" oifname "wg0" accept

And also require a new output chain in the router-fw table:

chain output {
    type filter hook output priority filter; policy accept;
    accept
}

This is what I have come up with so far. Is there anything else that I'm missing, or doing wrong?

(edit: switched git reference from master to a specific commit)