Well torrents are slow, typically, and unless the video you wanted to watch had i high amount of seeders, that can cause issues. When i use it, i sort by the number of seeders, and then find the highest balance of quality vs seeders.

You can disable and tweak transcoding settings, but it might mean that certain media isnt going to be able to be played at all, if its a certain format. If you have a beefy computer, this shouldnt be an issue, but if not id check this out: https://jellyfin.org/docs/general/server/transcoding/