Ohm's law
Amp = Voltage / Resistance
Joule's law
Wattage = Voltage * Amperage
Combined
Wattage = Voltage * (Voltage / Resistance)
For VV mode, you change the voltage output of the device in efforts to change the wattage (power/heat).
As an example, if you have a 2.0 ohm atomizer and have the setting on 4 volts, your total power = 4*4/2 = 8 watts.
If you increase the voltage to 6, then you've increased the total power from 8 watts to total power = 6*6/2 = 18 watts of total power.
VW mode works backwards from VV mode. You first decide what wattage (power/heat) you want as your output first. Then the device reads what the resistance of your atomizer is, and finally decide what voltage to apply in order to achieve the wattage output.
As an example. If you have a 2 ohm atomizer, and have the setting on 8 watts, the device will give an output of 4 volts to reach that setting.
If you change your atomizer to 1.5 ohm, the device will change the voltage accordingly down to ~3.5 volts to still give 8 watts.
VV settings are good if you want to make small adjustments to your vaping experience.
VW settings are good for "set it and forget it" type of vaping experience.
Careful with VV settings if you switch between high and low resistance atomizers. Forgetting to adjust the voltage accordingly will result in potentially burning the atomizer, juice, or coils.
With either you can control output power equally as well. With VV you must change voltage manually when you switch to an atomizing device of a different resistance. With VW you can switch out devices of different resistances as often as you want and not worry about adjusting voltage. That adjustment will be done automatically by the APV to give you your desired power in watts. VW is just a smarter and more convenient upgrade to VV. With VV/VW you have the best of both worlds.
Using the Sigelei in VV mode can allow you change your output power in smaller increments than with the VW mode (.1V). However, most users find the .5W increments in Power (VW) mode to be more than sufficient.
So basically the VW will only need to be set once if I use the same juice in atty's with different resistance.
VW is only "set and forget" if all you're using are single coil atomizers. Once you introduce dual-coils atty's, VW "somewhat" flies out the door. You can read THIS for an explanation of why that is.
I use dual coils all the time with my Vamo and never have an issue. That explanation (if somewhat correct) does not negate the advantages of VW. And I don't have to have an electrical engineering degree to know that dual coil atty/cartos provide fuller/warmer vapor on an APV that can handle them, like the Vamo.
I've owned several VW devices, IMO the so called benefit of VW set it and forget it is hog wash.
In my case 3 different flavor juices (same pg/vg and nic) in 3 of the exact same delivery devices.
Set it for the tobacco flavor then the 2 other flavors taste burnt, set it for the fruit / lighter flavors the tobacco flavors lacks in all areas of vape quality.
It is still necessary to fiddle / adjust constantly if you switch flavors frequently even when using the same exact ohm delivery devices.
That explanation is not "somewhat correct"... it is correct. I really don't feel like arguing electronics with you, but if you took some time to learn some basic electronics, (specifically ohms law for parallel circuits), it might make sense then. In the mean time, you can believe whatever you wish. As I stated in that write up... "Some people may not be able to tell the difference because you are still vaping at 9 watts total." The writeup is to explain misconceptions about dual vs single coil power and how it's related to VW. You cannot simply state that VW is set and forget in all cases... to do so is misinformation. That fuller/warmer vape you're getting is just your perception because one of the dual coils is sitting closer to the top of the carto.
Then my "perception" (which I don't agree with your characterization) along with hundreds of other vapers on the performance of both VW vaping and dual coil attys/cartos, is opposite yours. I've vaped on approximately 25 different PV's along with just about every attachment one can use, and know the difference in performance. Your experience I'm sure is "vast" based on vaping for all of what appears to be a couple of months. My electrician friends who vape actually agree with my "perception". And the electrical engineer who developed one of the first VW models on the market also agrees with my "perception". But hey, with your vast experience and electrical background, I'm sure we (including the electrical engineer with a degree from MIT) must be wrong and you are right that there is no difference in performance and dual coils don't work well with VW.
I've owned several VW devices, IMO the so called benefit of VW set it and forget it is hog wash.
In my case 3 different flavor juices (same pg/vg and nic) in 3 of the exact same delivery devices.
Set it for the tobacco flavor then the 2 other flavors taste burnt, set it for the fruit / lighter flavors the tobacco flavors lacks in all areas of vape quality.
It is still necessary to fiddle / adjust constantly if you switch flavors frequently even when using the same exact ohm delivery devices.