I’m pretty sure this is explained somewhere, but unfortunately I haven’t found it, so I apologise in advance…
After a download is done, it’s renamed and copied to the correct file. However, where do I set how and when the torrent and the episode are deleted from their original location?
On Download Client Settings you can enable Remote for Completed Download Handling (advanced option) and Sonarr will remove them when it finishes seeding (meets the seeding ratio) in Transmission.