In the menu bar go to help > troubleshooting information. In the page that opens there 8s a link to about:profiles. All details are available on the mozilla website. https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-thunderbird-profiles

You may create multiple profiles in Thunderbird and open only the one you want selecting it in about:profiles

Port forwarding allows connecting to peers who have not set it up (for both leeching and seeding). Two peers without port forwarding can’t connect to each other, if you set it up you can connect to every peer in the swarm. Torrenting behing a VPN always hides your real IP address😉