Both Sonarr and Radarr have options to either copy files (which leaves the original in place) or move files (which should delete the original but I haven’t tested this to be honest).
If you delete the file from your complete folder it will stop the seeding. The AutoRemovePlus plugin is what I use to control when the completed torrents get deleted. It has settings for seed time, number of torrents, minimum disk space, seed ratio and probably a few others.