WebTorrent is a streaming client. I recommend not to use it without a VPN due to possible legal issues.
WideVine is a digital management rights from Google. It restricts access to content that is copyrighted.
If you do not use any, there is no reason to enable the extensions.
Torrent protocol allows to see who is connected while downloading/uploading or streaming. In some countries, users have been receiving letters from lawyers with some huge fines to pay due to download/upload of protected content. If they do not pay the case is sent to court. This is a trend in many countries.
A VPN hides the real IP address, making it much more difficult (but not impossible) to identify the user.
Torrents are useful for downloading really big files by cooperating with others also downloading. If you use Brave to do this, it takes care of all the details under the covers for you.
The torrent protocol is notoriously often used for copyright violating downloads of (for example) movies and popular music.
But if you want to take it out for a public domain respecting spin with no VPN, try one of the torrent links at https://archive.org/