Proton VPN: Clarification on setup for port forwarding

[Splinter7914]

Looking for a new service provider with port forwarding and was thinking about using Proton VPN. Need some clarity on how to set this up. I am seeing previous discussions/issues where folks have custom scripts to manage ports so I was not quite sure what the expected behavior is in case I need to revisit what provider to use :).

protonvpn.md#required-environment-variables

mentions VPN_SERVICE_PROVIDER=protonvpn how ever the tldr wirguard setup also says use custom provider.

So not sure if I need to set service provider as custom or protonvpn. Does the statement on filtering still apply? So if I wanted to filter on P2P that would not be feasible for Wireguard? I assume this means I need to set the key for the P2P server itself?

So in my setup I would need to specify the following variables

## various Wireguard variables
VPN_SERVICE_PROVIDER=protonvpn or custom? # Not sure if I need to use custom or not.
VPN_PORT_FORWARDING=on
VPN_PORT_FORWARDING_PROVIDER=protonvpn
VPN_PORT_FORWARDING_LISTENING_PORT=some static number? # This is what I would add in qbit and it would dynamically forward to the actual port that was opened?
FIREWALL_VPN_INPUT_PORTS=Do I need to set this? I think I was using this back when Mullvad allowed port forwarding.
FIREWALL_INPUT_PORTS= Does this need to be set?

Is this correct? So with this even if Proton VPN port changed my configs would not?