You can torrent without portforwarding. The only issue is on rare Linux isos. You potentially will have trouble discovering new peers. At least one person will need portforwarding.
It's more that effective seeding is very hard without a forwarded port. If you only leech, you'll be fine. But that's not how the system is envisioned.
I linked a Docker Container elsewhere in this topic that works with Proton's implementation of port forwarding. Proton's price is the same as Mullvad too. That would be my recommendation.
Had to leave MV because of this. I went to Proton, though I did need special software to support its form of port forwarding without introducing a regular hassle. All good now, mostly.
I was looking at Proton too but I'm already a customer and the VPN is going to be shared with family members. I worries if they can access my mail if I share my account.