Questions about VPN (Mullvad) port forwarding?

[JG76]

My understanding of using a VPN with port forwarding is to allow devices (say a phone or laptop) to connect to a VPN endpoint and port, and have that connection forwarded on to the device hosting the wireguard connection with that endpoint.  Is that a correct use case?

If so, is the external / incoming connection to the VPN endpoint and port required to also be connected to the VPN?  Or can it be any external connection (for example an app on your phone like Blue Iris that is trying to connect to the home server via a cellular connection)? Does that make sense?

I'm asking because I have some P2P networking software running behind an OPNsense router with Mullvad (not torrenting) that I would like to have external peers connect to it via the VPN's port forwarding. If my understanding of the basic concepts are correct, then it seems like this should be doable?

I have made some attempts at configuring the above with mixed results (depending on the client in question), but wanted to sanity check things in here before going any further.

Thanks.

[zan]

Basically you need double port forwards: From your VPN provider to your router's tunnel endpoint address, and then from your router's tunnel endpoint address to target address.
If Mullvad allows you to set port foward to your tunnel IP then it should be doable.