In VV you set the output level of the
mod, regardless to whatever atomizer is attached. (variable voltage) While older mods supported this it is rather rare in modern mods.
In VW you set the output wattage of the
mod, taking into consideration the atomizer that is attached. While the output voltage will change depending on the resistance of the atomizer attached, it will maintain the same wattage value. All modern mods support this mode and usually call it "power mode".
g.