The question as originally asked does imply a two dimensional situation, although one can easily imagine ways to make things more complicated.

For any "real world" wiring problem, the questions of whether the wires (or their insulation) well melt when you put too many through a tight hole, and whether the crosstalk between wires kills your circuit function are likely to be of about as much significance as whether the hole is the "minimum geometrically possible" size.

John