An old Xeon system uses a lot of Electricity and generate a lot of heat. I would recommend looking on eBay for as more suitable pc. A PC that will support windows 11 like an 8th gen I7.
With substreams now a thing, darn near anything will work.
Folks are running 50 cameras on a 4th gen.
But if you are looking to buy, unless you get something free or cheap, like the member here that picked up a 4th gen for $25 at an auction, the minimum you would want to go with is an 8th gen so you can run Win11.