Home NAS for sharing files with family in Europe?

[Enquiries]

I am looking to get my first NAS
It is for my home; the idea is that I can stream my files to my TV while also sharing with my family at home in Europe

I want to get a DS920+ and some HDs

I need advice on which HDs to get - Seagate seem the best, but Synology also do their own, and I don't know which might be best

My concerns are my limited tech knowledge in assembling a system like this from scratch
And also being able to set up a network where I can stream Plex to my TV, as if my NAS were just another service


Apologies if these questions are super basic

Thanks

--Sean