My (possibly mistaken) understanding is that during the download phase your client is contacting seeds requesting parts. Although the data is going to be incoming it’s still an outbound connection because your client initiated it, so you don’t need to be connectable for that.
It’s the seeding phase which is problematic because downloaders can’t contact you to request parts. That said your client will still contact downloaders and offer parts, which again is an outbound connection so you don’t need to be contactable.
In summary download speeds are uneffected, but seeding rates will be diminished. With most private trackers you can still satisfy seeding requirements just by keeping the torrent available for however long.
As an aside I use mullvad & wireguard. I’ve found wireguard dramatically easier to configure, particularly in a docker environment.