he will use sectors, so the mentioned problems should not exist.
As far as I understand, using 3 RBs is to decrease load per machine.
He wrote the question very unclearly, not the mention the topic name.
More detailed info would bring better answer.
BTW, the problem exist with sectors if there are 60 connected users, we had that problem on many places and it was pretty bad idea - besides that clients switched to sectors with lower signal, it happened that if AP is restarted the radios couldn't start to work for hours on busy APs (with 60-80 connected users) becouse clients switched the sectors constantly. After changing the SSID names all worked fine.