ThinkCentre M70q

the N97,N100,N150 processors tend to reach 100% CPU load during mid-heavy task so if you plan to use it for plex only nothing else it should be fine My used Lenovo M70q tiny been runing 24/7 for years now as a plex/jellyfin server just fine can do multiple 1080p streams at once and one 4K at a time

All of those models are REALLY old. The Dell OptiPlex 7010, 790, and 9010, are from the early 2010s and are only DDR3. The Precision T5500 is a workstation from the same DDR3 era but only accepts ECC RAM. Workstations typically have different processor, ram and other options compared to consumer dev

I guess it depends on the use case. My kids do game stream (Sunshine/Moonlight) so codec support was important and therefore we went with NUCs (12 Pro I think). For my homelab, I went with two Lenovo M70Q Gen 3. Quiet, small, easy to upgrade and quite thrust worthy brand. Those can be found for €250

Lenovo Tiny PCs. ThinkCentre M70q Gen 5 We sell a lot of these to our clients, along with a matching 24 or 27 inch monitor that the PC plugs into the back of. These will keep you going for the next 5+ years. They also have a ThinKiosk mode if your on a Citrix environment.