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Stacking Factor refers to the overall total ratio.
Knock yourself out laying th wires down carfully versus simply wrapping them. I would be interested to find out how many more turns ou got on there by being so neat.
The time when laying wires down carefully really becomes important is when you're winding a high voltage coil, or a high frequency coil. In the HV coil you need to make certain the voltage gradient along the coil is minimal - in other words, keep the voltage between overlapping turns very low to prevent it from shorting out. In the HF coil you need to pay attention to the interwinding capacitance, else the self inductance comes way down on you. The two kind of relate.
This compnay carries wire down below 56 Awg and has some tables and charts that list min/max diameters for all types of wires. hey had the most realistic values for realizable coil winding I've found.