Hello!
Here is my current setup and what I am looking for from my next one:
Currently have a Nvdia Shield with a 4 and 8 TB HDDs attached to it directly. So far this has worked well for 2-3 remote streams of 1080p content.
I’m looking to upgrade to a Beelink off Amazon which would allow 3-4 4K streams and a HD enclosure that would allow me to attach my external HDDs and start a NAS. Please advise on how to proceed from here.
In general for smaller servers I actually recommend starting fresh for the new server rather than trying to transfer your metadata over, but if you want to try the instructions are here that's just if you want to maintain any custom matching data, watched status, preferred languages etc etc.
You can run it on the out of the box windows install if you aren't comfortable linuxing (though I'd suggest something like proxmox or ubuntu) just install plex server, plug in the old HDDs, map the new library locations then set up plex player on the shield to point to the new server (hardcode the IP in plex players settings if you have trouble)
As for the hardware itself, if its just plex and the usual ancillary apps that go with it you can use an N100 or N95 and get plenty of performance for more than 4 clients as long as you don't need to transcode too much.
If you need to transcode 4x high bitrate 4k streams at once comfortably you definitely need something a bit beefier than those little CPUs (mostly they are memory and cache limited), but not much more, you don't need an i7 for it, just an i3 or i5 class cpu will do.