Hi Drifter,
First, to keep it simple, just adjust the voltage or watt setting on your device to whatever gives you the vape you want. That will vary depending on the coil resistance and the
juice, and there is no "right" setting, other than the one that pleases you. That's the "perfect taste and vapor" - and what you like may not be what I like, eh? (I like my steak rare, my wife hates it that way. Who's right? The one eating the steak!)
Second, in general, if you run at a higher voltage the battery will last longer between charges, as the higher voltage allows for the same wattage at a lower current, so less drain.
The higher the voltage on a given coil, the higher the watts consumed, so, yes, it can destroy a coil. The usual procedure is to start with a low voltage / watt setting, and work up until it hits like you like it. (Or increase same until it starts to taste a bit burned, then back it down a bit.)
That said, since this is an electric circuit, Ohm's and Watt's laws apply. There are specific relationships between voltage, resistance and current. Watts = Volts x Amps, but of course nothing in the vape world is marked in Amps (except our
batteries, which are generally mAh rated, telling us how long we can expect the battery to provide power at a certain discharge rate.) We can calculate the amps using the formula amps = volts / ohms, but more directly, if you want to calculate the watts, get that by squaring the voltage and dividing that by the resistance.
Since now you're probably even more confused, just do it the easy way and don't sweat it. Start low on volts or watts, and work it up to taste.
Remember or jot down the setting that gives you a good vape. Any coil of the same resistance, use the same setting to start, keeping in mind that if the
juice is also different, you may want to adjust.
If you change to a lower resistance, you'll probably need to lower the volts. Higher resistance, higher volts.
If your device is VW, it will take care of that for you, although different juices may want a different wattage for best flavor.