You would adjust it up or down, exactly as you said. If it's too hot, harsh, or tasting burnt, turn it down a notch at a time until it tastes good. If too weak, turn it up a notch until it tastes good.
You've asked a good question that many don't understand. With VW, a Voltage is what goes to the coil, just like with VV. But the Voltage is set by the unit to supply the Wattage that you dial in, according to the Ohms of the attached device. It has a Max Wattage of 12.5W, and a Max Voltage of 6 Volts, and also a Max Current of 5 Amps (with a 7 Amp Fuse). These are three Max limitations. I don't know what the lowest Ohms of a coil can be, but that's another limit. I haven't seen that stated, but 1.7Ω should be fine.
Watts = Volts x Amps, and also Volts2 / Ohms (that's Volts Squared). All three come into play. But your adjustments are to set the Watts you want, and the processor sets the Volts according to the Ohms, via the 2nd formula. Mathematically, it works like this...
The Volts you'll get = the Square Root of (Watts * Ohms). This is actually what the processor calculates (the Volts). It knows the Watts you set, and it knows the Ohms of the coil. If the Volts tries to go over 6V because of the coil, there's a limit that it cannot go above 6V, so 6V is all the coil will see, and you won't actually get the Wattage you dialed in. All VV and VW devices have limits similar to this. Some can go higher than others.
So depending on the Ohms of the attached Coil, you may or may not get the Wattage you wanted.
But for you at 1.7Ω...
7.0W at 1.7Ω = 3.45V
8.0W at 1.7Ω = 3.69V
8.5W at 1.7Ω = 3.80V
9.0W at 1.7Ω = 3.91V
9.5W at 1.7Ω = 4.00V
So you won't be close to the 6V limit.
And this is my third pair of them. I always get compliments on them when I wear them. (from other old ladies. 
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I like 
