It's pretty intersting the variations you get with different gauges. For the round wire, I was going with the 32 AWG (.20mm). Nichrome 60 gives me coils around 1.4 Ohms. The Kanthal D in with the same gauge bumps that up to a about 1.7 and the Kanthal A-1 bumps it up to about 1.8 Ohms.

The different materials have different resistances. The metric resistance constants are 1.1, 1.35, 1.45 for nichrome 60, Kanthal D and Kanthal A-1. To find resistance per meter, just divide the cross sectional area into those numbers. What's interesting is the Kanthal D and A-1 only differ by 1% aluminum, but it makes a notable difference in resistance.

I tried 30 AWG and 28 AWG nichrome but I had to use more turns to keep resistance up. I also found I needed more power with the heavier wire. Makes sense since you need more current to get a thicker wire up to the same temperature. I think the temperature of the wire is where the rubber hits the road in making vapor.

Now I'm using the .4 x .1mm Kanthal ribbon. The D ribbon I have is a bit wider like .42mm and gives me coils about 1.2 Ohms. The A-1 ribbon I have is closer to .35mm and gives me coils about 1.5 Ohms.

I usually vape around 15 Watts (4.2V) with a 1.2 Ohm coil using the Kanthal D ribbon. That's in my gennies. In my drippers, I'm using the A-1 Kanthal to get resistance up to 1.3 Ohms. The drippers run hotter than the gennies so I need a little bit higher resistance and a little less power.