it might work but jgreco, the guy that wrote the truenas 10gb primer, called it garbage.
yup nvenc should be more than adequate for plex but we usually recommend intel cpus for the lower power draw vs amd cpu + gpu.
I get not wanting to deal with 13th and 14th gen. its why i usually recommend 12th and older or the new core ultras.
How much it matters really depends on your power costs, for me with my shit rates itll cost me close to $40 usd a year just from gpu idle costs.
if this is your OS drive, i would recommend spending less and getting a smaller drive as OS drive doesn't really benefit from being larger than 16gb as the rest of the storage is locked out.
you can save your self a bit of money getting arctic p8 max or p8 silent fans, both highly rated.
80 plus efficiency means almost nothing for us homelab nas users as our systems will be at idle most of the time.
Check out this article of best psu's from the ppl that do the cybernetics ratings
You want to scroll to the graph for idle 20-80w power at 230v (assuming your are in australia)
and just find whatever has the most efficiency.
in general psus that are rated for smaller loads tend to be more efficient at 20-80w