First off, CONGRATS! I know you must be excited to be taking the next step as a breeder and what a great feeling that your hard work is paying off.
I didn't really notice any difference between having a stud vs a neutered boy until
after they'd actually been used as a stud. And I can assure you, no amount of discouraging them not to mount a female had any effect on their willingness to do so when presented with one in heat. The major differences I noticed was that they seem to have a tendancy to mark in the house afterwards. (But it always seemed to be quickly remedied once they were neutered later on.) Also--and this drove me crazy--my one guy would pant and pace alot after having been studded. Sometimes for no reason, but typically when someone came in who'd been around another dog--any dog, male or female, intact or not.
Best of luck again!