Dietpi is pretty good to get up and going in a day or so. Loads of videos on youtube for setting up various services too :)

Open media vault might be an option over dietpi but I've never used it myself. Again, lots of youtube documentation:)

If you want to stream torrents, you can use stremio and torrentio which let you stream the content of a torrent instead of download, but depending on the media you watch youll find it difficult to get enough seeders to download it fast enough to stream.

The benefit of running the downloads over streaming is that a poorly seeded torrent won't ruin my viewing experience since by the time I view it's stored locally.