The service I used to use shut down about six months ago and I’m yet to find a good replacement. So if anyone wants to put some words in my mouth (ugh, not sure I should have gone with that phrase) I’ll gladly accept. Seems like most of the “recommended” ones are referrals to scams, or have weird limitations (like not making the M3Us available, so you can’t hook in to Plex, for example).
Plex can be set to auto delete. You can set it to delete after something has been watched (after a delay if you want), or to keep a pre-set number of items (e.g. only keep the five latest episodes of show X) or a combination.
Just make sure you set up the *arrs to not re-download the thing that Plex auto deletes.
I’m a hoarder so I keep a lot, but anything that’s time-sensitive like current affairs shows, I delete after watch and set to only keep the latest three episodes.