Not really answering the whole question, but you really don’t need a lot. Currently running jellyfin, a blog and some other fun dockers on a raspberry pi (clone), with an external nas though a large USB would do. Start with just “retrieving” movies to your local disk and think what else you need.

• want to access movies between devices? Get some cheap server (I.e some second hand computer) or a NAS
• want to have some snazzy UI? Get jellyfin
• Want to be able to expand storage? Set up some raid configuration or similar.

Good story about overcomplicating things