Personally I got a Qnap TS-212
This is used to only store movies, and then i use a small tower this is a pc that runs windows xp normally so its about 8 years old.
Running docker and have everything. I'm running for movies, Radarr and for Series i got Sonarr.
So the server only downloads the files and controls where they go on the drive renames files etc.
It also has a MySQL database to store where in movies i am so I have full pause, resume functionality across devices.
The NAS is only used for storage.
For players I use 2 Raspberry PI one in the bedroom one in the living room. Both running libreelec which is a fork of Rasbian with Kodi.
Works great and Everything is one button away.
Any device on my home network that has Kodi can now watch and resume straight from the NAS.
I can configure and open the port to have 3g/4G playback but havn't seen the need for it.
As a added bonus I use my 4x Google Home mini so i can issue voice commands to play, pause, resume movies on any device.