The *arr stack was a pain.

You'll need prowlarr for downloading. And a Bittorrent client that works with it (e.g. Ktorrent doesn't).

Then you'll set up radarr/sonarr, and ensure they can talk to prowlarr.

Setting up Plex is straightforward. But I think you do need to make it visible to radarr/sonarr.

It was definitely a pain, but once I had it set up it's been fine.

>But I think you do need to make it visible to radarr/sonarr.

Sort of. You tell Plex where your directories are for movies and TV shows. All you have to do with Sonarr/Radarr is have them dump the finished downloads into their respective directories.