You should look into hard linking: https://trash-guides.info/Hardlinks/Hardlinks-and-Instant-Moves/. Remaining and no double storage

As for trakt isn’t that what you want? If you haven’t watched it and it’s on your watch list why filter things out?

It’s not cheap but building a nas from scratch is loads cheaper. Looking up NAS killer 6 on serverbuilds.net have some great guides and support

Why would you want to move your content off Plex once the download completes? How would you watch that content then?

Bazaar has an option to download based on things not in sonarr or radarr so you can use it with base Plex.

Buckets is good. Does require some setup for automatic import. You can also use the simplefin bridge if you want something automatic. Does cost though if you go that route

IRC is where I get most of mine. IRC highway and evooks