What's the limit on the number of cables allowed through a single entry?
My experience has been "what will fit", based on my practice and no AHJ complaints ever. I routinely insert three 14/2's or 12/2's in a single-gang Carlon cable hole when they come from the same direction, such as feed-in/feed-out/switch-leg to a wall switch.
In fact, when roughing, I usually strip the two or three cables, strip the wires, hook those intended for screws, align the colors, "pre-twist" the grounds together (and any others to be joined) all before inserting them into the box, and then staple or stack.
To me, this is faster, and definitely neater, than any other way; especially compared to others I've seen who don't even strip the sheath before box insertion. Plus, I never mistake which wire is which (leg, travelers, etc.) I also label the cables inside the box.