I'm not sure I fully understand your setup or what you are trying to accomplish so apologies beforehand if I misunderstand.
One option would be to host the wg server on your SBC (guessing a raspi or something like it?) and make the VPS a peer thus routing everything out your home network. You can also use AllowedIPs to only route specific ranges on the wg network which allows other traffic to follow the route tables on that device and exit accordingly.
But if what you are asking is how do you have different peers on a wg network route their traffic out to the internet on various different peers you're going to need to get fancy with routes/iptables/virtual network interfaces/policy based routing using PostUp commands.
One option would be to host the wg server on your SBC (guessing a raspi or something like it?) and make the VPS a peer thus routing everything out your home network. You can also use AllowedIPs to only route specific ranges on the wg network which allows other traffic to follow the route tables on that device and exit accordingly.
But if what you are asking is how do you have different peers on a wg network route their traffic out to the internet on various different peers you're going to need to get fancy with routes/iptables/virtual network interfaces/policy based routing using PostUp commands.
Hopefully that gives you something to go on.