Port forwarding will allow you to receive connections from clients that are themselves behind NATs, and would also allow you to participate in DHT which would allow you to discover clients faster.

Though in ideal cases (ones with high active seeders), that isn't going to affect performance that much. Torrent can also use UDP hole punching, but that can sometimes be finnicky behind CGNATs

Correct. At least one side must have an open port. So if that's you you can peer with everyone instead of only people with open ports.