In response to posts #3 and #4
Ummm...Not exactly. The "resistance" of a device refers the the impedance of the current, not physical resistance of the human body. Power changes temperature, which affects flavor and throat hit, but not airiness (although a warmer vape may feel less airy).
And at lower resistance/ohm/Ω the device will actually produce a warmer vape, unless the voltage is set low. Low resistance devices came on the market so that people with low voltage regulated batteries (like the original Joyetech eGo, which fires at ≈3.3v) could experience the kind of vaping as people using more powerful batteries. For example:
Let's take a Joytech firing at 3.3v. Matched with a 1.8Ω head, the vape would be ≈6w
The same 3.3v battery, matched with a 2.2Ω head will produce ≈5w
Variable voltage batteries allow you fine tune the power level to fit all of those devices.
For example, if you set the Twist at 4v (I tend to start there, since it's kind of the middle) your heads would provide:
1.8Ω - 8.88w
2.2Ω - 7.27w
2.5Ω - 6.4w
8-6w falls pretty much in the middle of where many people like to vape.
The actually calculation is voltage x voltage / resistance = wattage, but you really don't need to know that beyond conceptually.
Math and charts only give you a rough starting place. The point is just to pick one and dial up or down until in tastes good to you.