Firstly, Vamo user manual here:
http://www.e-cigarette-forum.com/forum/vamo/359600-vamo-vv-vw-v2-user-manual-download.html
Firs thing to do when you get the Vamo is put it into NO 2 mode -which is the accurate RMS mode.
Variable wattage: You set the watts on the display e.g. 7 watts. The Vamo reads the resistance of your attachment, and automatically sets the voltage to give 7 watts. For myself, I prefer variable wattage over variable voltage because I can switch from one accessory to another and stay at the same watts. Or I can adjust watts and not worry about calculating whether the volts are ok with the ohms - the device adjusts the volts automatically to the right level.
I can also adjust watts with different juices, and again not worry about volts and ohms being mismatched since it adjusts the volts automatically. Since I have a lot of different juices this works well for me. Sometimes I just change the watts with the same juice - depending whether I want it a little cooler, or I feel like getting the warmer taste. I like some juices at more than one temperature. So I adjust the watts, which is the power, with a simple click or two and vape.
Its a more convenient, cruise control way of setting the temperature of your vape.
Not getting sick of you - I'm glad you have had the initiative to ask about these things.