I was not able to find any benchmarks on that one, but you assume correct.I was asking about these types of CPU's: Gold 5222, Gold 5217, Silver 4215R (3.2Ghz / core ). I added this Silver CPU because it has good speed / core and only has 8 cores. If I understand correctly it is way better to have with less core but with good speed / core. But why is this Silver 4215R CPU is worse than Gold 5222 or even Gold 5217?
Xeon Silver 4215R CPU will likely do much better than Gold 5222 or Gold 5217.
I will have to take a step back back on some Silver Xeons R's as if I recall Intel decided to "Refresh cascade lake" CPUs by upgrading them with a lot better clock speeds (more like "rebranding" a solid Gold "previous-lake" to refreshed Silver or Platinum to Gold).
This Intel® Xeon® Silver 4215R Processor (11M Cache, 3.20 GHz) Product Specifications looks very decent.
You stated a legit concern about i9 not being a "server" CPU. That is mostly due to no support for ECC. I wrote couple of lines about that here Which are the fastest CPUs for PHP websites like Wordpress and Magento / Development - Klik-MALL.com
under "Does it matter that i9 CPUs do not support ECC memory?"
If it's a single-machine setup as yours, you are right, go for something with ECC ram.