Cool! Glad you like it.
Sounds like the tank is a top coil unit. Could be in the CExx line, or maybe an Innokin IClear... The string is the wick, and the coil is near the top of the clearo. Other things being equal, tp coils usually give a slightly warmer vape than bottom coil ones. Which type to use depends on what you like
You can select either variable voltage or variable wattage mode, not both. Both achieve the same thing - letting you control the power (heat) to the coil. Different resistances need different voltages to have the same heat. Same heat, same vapor. And some flavors taste better at different heat.
So in VV mode, you directly control the voltage. In VW mode, you tell the mod what amount of heat you want, and it automatically controls the voltage for you. That way, changing coils, or to a different topper, the mod still delivers the same heat to the coil, and your vape (theoretically) tastes the same.
Whichever mode you choose to use is fine - it's your mod
To get a feel for how the changes work, do this.
You're already set pretty low on volts, so increase volts by about 0.2, and vape.
Like it? Repeat the step.
Repeat until it starts to taste "off" and then back off a step.
You're done.
(Typically, for most clearo type toppers, somewhere between 3.2 and 4.2 will start to be pretty good. 6 does seem a bit hot! But lots of variables there, flavor, viscosity, condition of coil and wicks...)
If you choose VW mode, the procedure is the same, although the step will be 0.5 W, vs. 0.1 that it can do on VV mode. Start low and work up in steps.
I'd get used to what you have on hand, decide on top/bottom coil, pyrex clearos. Get comfortable before getting so much gear you're overwhelmed.