With a VV/VW mod, don't worry about keying in the resistance. The batteries have no clue what resistance atty is on there. If you are running at 150 watts, you are drawing 7.4 volts(the nominal capacity of the cells in series) at 20.27 amps. That doesn't get halved, because we used the 7.4v of the two cells together. When you are using a VV/VW mod, there are two circuits in there. There is the one between the battery and the chip, and the one between the chip and the atomizer. The chip will draw the voltage the batteries are at from the cells at however many amps it takes to get to the wattage you are wanting.
EXAMPLE:
If you are wanting 74 watts from the two cells in series which we will assume are at the nominal voltage of 3.7v each, or 7.4v in series, the chip is going to see that it needs 74 watts, and draw 7.4 volts at 10 amps(3.7v at 10 amps from each cell) to get 74 watts. You could have a 0.5 ohm coil on there or a 2 ohm coil. It doesn't matter. 74 watts is 74 watts. If you are running a 0.5 ohm coil at 74 watts, it is drawing the 7.4 volts at 10 amps from the batteries. If you are running a 2 ohm coil at 74 watts, it is still drawing the 7.4 volts at 10 amps from the batteries.
In other words, since you have a regulated device, stop worrying about ohms. As long as you are in the acceptable range of the device, that is what matters. All you need to worry about are the watts you are wanting to push through to the coils, and what voltage the batteries are at. That is why I said to base your calculations of the cutoff voltage of the device, which is 3.2v per cell, or 6.4v in series(you know your batteries will always be above this, so it adds in some safety). Take the number of watts you are wanting to push to the coils, and add 10% to that number(if you are wanting to run at 150w, add 15w to it for the device inefficiency to get 165w). Take that number(165w) and divide it by the voltage(6.4v) and you have the amps you are drawing. 165/6.4=25.8 amps.
EDITED TO ADD------
If you are running authentic Sony batteries capable of 30A continuous discharge, you should be safe to run it all the way to the 150w max it is capable of delivering. Even if we figure 20% inefficiency, that gives us 180w total being used, which is drawing 21.5A when the batteries are fully charged(4.2v each, making 8.4v in series), or 28.125A when the batteries are at the device's cutoff voltage(3.2v each, making 6.4v in series). Both of those are below the 30A CDR rating of the batteries.
