Big watts = big vapour.
Higher volt = higher watt
Lower ohm = higher watt
If you use vv (variable voltage) and if you set it to, lets say 4v, on a 2,0 ohms mizer, it will give you 8 watts. Volt x volt / ohm
If you put a 1,4 ohm mizer on that, it will give you way too many watts, and will taste burned. You will have to calculate: V = square (ohm x wanted watts) = square (1,4 x 8) = 3,3 v, and set your vv device to this, in order to get the same vape as 2 ohms @ 4 v.
A vw device does all this for you, and gives you the wanted watts with any ohm mizer.
Rms or not rms? Same same. Rms are "true" watts, and 8 watts rms are more than 8 watts not rms. Find the spot you like and keep it there