At the moment what I do, is extract by the client to the same folder of the torrent.
Sonarr copies the file (mkv,mp4, etc ) to final destination. A post import script executed by sonarr that checks for rar files presence in the source folder. If they exist it will delete the source file.
Just recently source folder and source file environmetal variables where added to sonarr. This is convenient in my case since i use a seedbox.
A setup with sonarr+downloader in the same host you’ll be doubling space usage if you extract.