Re: nyc addendum to the nec
The only requirement for stapling NM cable is that you cannot staple them on edge (assumng they are a flat cable).
As far as how many under one staple, the box should say. Most of the ones that I see are rated for any combination of 14-2, 14-3, 12-2 and 12-3, as long as the total doesn't exceed 2 under a staple. Again, check the box of staples that you are using.