Sorry. I'm a little bit more awake, but it's best to think of the stack kind of like this.

Whether you're getting torrents or .nzb files (usenet / news rooms) youll need a client for them to download. Sonarr and radarr are...Coordinators. they help search your indexs l, grab files, give them to your download client, then can move, rename and Organize them for you when they're done downloading.