Just got a great deal on a Dell Precision 3420 with a Xeon E3 1270v6. It has 4GB of ram but I intend to upgrade it soon to at least 16gb.
If running VMs and containers, how far could I realistically go with 4C8T from 2017? I was thinking of at least running OPNsense with a new network card as well as maybe TrueNAS, but I'm not sure if I could realistically run more, like a Plex server for a few people and myself.
You will moust likley run out of ram before you hit the 80%cpu utilization even with 16G of ram :) Also all the services you said are perfectly fine and you will even have room left for more services