Lower resistance = more heat, and Nicotine is absorbed faster (and felt more) by the body as heat increases, which is why you get a stronger Nicotine "buzz" and more throat-hit from Nicotine if you lower your resistance of your coil (but don't lower the % of Nicotine by the same amount).
@Tam's example is spot-on... she dropped her coil resistance by 75% (roughly), and needed to drop her Nicotine by the same 75% (12mg to 3mg) to get the same "feeling", and the same Nicotine absorption.
Nicotine absorption rate is a little complicated (math), but the basic rule-of-thumb for vaping is, if you lower (or raise) your coil resistance by X%, then you should lower (or raise) your Nicotine level by the same X%, to maintain your absorption and Nicotine feel/effect. The relationship is nearly linear above 0.5 Ohms, with a steeper curve below 0.5 Ohms because power and heat increase more as you approach zero resistance.... This is why Temperature Control devices have become more popular for those who sub-ohm 0.5 Ohm coils and lower TC devices allow you to control the temperature / heat, so you can (for the most part) use the same juice with a 0.5 Ohm coil as you do with a 0.2 Ohm coil, but you'd still find a lower Nicotine level more appropriate (even when using TC-mode) with a lower Ohm coil, than you would with, say, a 1.2, 1.5, or 1.8 Ohm coil.