FWIW, and I'm not sure if this is against terms here, but I use newsgeek for the former and giganews for the latter. Both are paid services but reasonably priced imo. When I can find something on Usenet, it typically downloads with speeds > 10MBps vs. torrenting which can exceed that but is usually much slower.
You can use whatever client you want. I have the *arr stack mentioned elsewhere in this thread as well and SABnzbd is the recommended option there.
This slightly outdated guide helps you set it up pretty easily - instead of Zurg+ Black hole, use Decypharr
https://savvyguides.wiki/sailarrsguide/
Real-debrid == imagine a huge cloud storage service. You have 1000 people trying to download Burgonia.4k.mkv. it downloads the torrent once to the shared server, then gives each user their own access to it via a WebDAV mount.
WebDAV == trick you server into thinking a cloud server is a local folder. You use RClone to mount this and it's accessible from your local drive so you can stream all your stuff directly.
What this means: you add a show in Sonarr or a movie in Radarr. Prowlarr searches Torrentio or Zilean for torrents. The best match is chosen. It sends to Decypharr (or black hole) to say "download this torrent to my real debrid box". It finds the cached version of the file, which is instantly available in your drive. It's symlinked so Plex can pick up the file.
Basically the lead time from requesting a movie/series to watching it on your tv is about 10 seconds, with no storage overhead required.
It's also a lot less prone to failures than debrid services, especially with old content.
And I don't have to play the 'which service has this?' game.