Yeah the device limit is annoying. I switched to AirVPN when Mullvad stopped doing port forwarding and it’s been fine so far. I’m not a network expert so I honestly don’t know the difference between the two protocols enough to say that they’re any benefit of one over the other, but there might be a reason that WireGuard is becoming the default? Idk honestly.

Anyway, AirVPN still suports port forwarding and supports OpenVPN so might be an alternative for you. They don’t do security audits which is imo sketchy and makes me question if they are honest about their no logs policy, but otoh they have been around for a long time and there hasn’t been any incidence, which makes me think they’re probably good enough for torrenting.