I finally got around to putting all the pieces together for my QS box, and am quite pleased! Standard HP290 with the Celeron G4900. Added 2 x 8 gb sticks of ram, which is way overkill, 4gb is probably enough, 8gb is definitely plenty. Removed the 500 gb drive and the 2230 wifi card, no point in haveing those for this use case. Added a 256gb m.2 nvme, which will be more than enough for the OS + Plex data.
I did my initial install on 19.04 desktop per JDMs guide on a 16gb nvme for a couple weeks, but am trying out 19.10 server for now. I hope to move over to the 20.04 LTS when it comes out in a couple months and then not touch this for a couple years other than minor version and security updates.
I expect a couple days of monitoring and tweaking; a few odd NFS and apparmor kinks to iron out - no biggie.
JDM - thanks again for the recipe!