Mullvad stopped doing port forwarding, so searching for alternatives.
Yes as far as I’m aware you can only leech via i2p what is seeded to i2p. Maybe one day the outproxy system will be more like tor exit nodes and allow leeching clearnet torrents from i2p.
But you can seed to both. So if you’re already seeding in the clear (or via vpn) and your bittorrent client supports it then you might as well also seed to i2p.