The end UI is super simple. Search for a movie. Click Add. The software takes case of the rest. It automatically downloads the movie and replaces it with a higher quality version when one is available.
TV: Switch out Radarr for Sonarr above.
Music: Still working on this, but set up an MPD server on the NAS and listen using an MPD client on mobile. A good client seems to be Rigelian for iOS.
All super easy to set up. All the software is dockerized (check the linuxserver docker repo for most of this) and secure to access - set up a VPN server on your NAS and use a client like Tunnelblick on Mac or OpenVPN on iOS to access it.
So now I can have lunch with my coworkers, and if we're talking about a movie that sounds interesting, I open up Radarr on my phone (it has a nice mobile web interface), search and click download. It'll be ready for viewing in all its Blu-Ray HDR10 7.1 surround-sound glory by the time I get home.
Some Docker images you might find useful:
1. https://hub.docker.com/r/linuxserver/sonarr/
2. https://hub.docker.com/r/linuxserver/radarr/