Projects are fun. Do it if you don't mind failing. Just keep failing until you get it right.
Wdrussell1
The setup is not ideal, I won't lie to you. It could be better. But honestly, if it works for you, do it. There are so many things you can do to improve it and generally it will serve as a stepping stone to the next upgrade you see yourself making.
I will also note, since you have two of them, you could take the proxmox route and make them redundant. I am sure there is a way with Unraid to make them redundant too. I really wish I had the knowledge to run things in RAM.
I thought for a moment this was in the wrong sub. At this point I think your friends mom needs some taking care of around the house.
For Plex specifically it is a pass. This will have Xeons and Xeons don't support quick sync. You are going to be much better off buying one of those micro desktops from Dell/HP/Lenovo.
What I want to see is this thing fit 7 Nvidia Tesla T4 16GB cards in it. HP says it is possible in the data sheet.