Up to 64 that should be good enough, however, I would opt for a consumer CPU instead of a Xeon - a FiveM server only uses 4 threads IIRC, so you want to have them run as fast as possible by having the highest clock and boost speeds which server processors don’t offer.
I dont quite understand the question sorry
are you trying to host the server at your home or what
i would opt for used Ryzen or new i can get here a 5800x for 130CHF some cheap B450 Board or maybe even 550
something like this: https://pcpartpicker.com/list/pwqycx
Maybe change out the RAM for ECC Ram since CPU and Mainboard support it but yeah ¯_(ツ)_/¯