You seem to be a little confused, NO1 and NO2 mode are completely separate from VW and VV modes. You always want it in NO2 mode, because that is RMS mode, and is generally just safer.
You hold both the + and - button to switch between VV and VW mode.
As for what to have it in, I guess it's personal prefference. With my dual coils, I like to manually control the voltage, because I KNOW that it's being divided into two coils, your VAMO however doesn't know that, it reads 2.0 Ohms and just assumes it's a single coil. But again, this is personal prefference, when you get down to it VV and VW will do the same thing, it's just that VW gives you a little more control, as it's got more options for fine tuning.