I'd suggest separate systems for NAS and media serving.
I've a Ryzen Embedded system with lost of RAM as my NAS box and a small Intel N-series based system as my Plex server that pulls media off the NAS box.
You can, but for media serving and transcoding you ideally want Intel Quick Sync, and it's simpler to have separate systems for your Quick Sync system and your "many cores" system.
Both of the CPUs you mention are low-power I don't think this a problem for slightly meatier processors unless you need the GPU or Quick Sync for multiple purposes?
