You need Ohm's law, probably for the first time since O level physics
This is from one of the old 'evangelical' threads on AIBU ...
Resistance ... it's all to do with Ohm's law - V=IxR or I=V/R or R=V/I
So what does that mean?
V is voltage. A standard eGo battery is 3.7V. This is what you can change with a variable voltage battery.
R is resistance. This the ohm value of your coil. Most seem to be either 2.4/2.5ish or 1.8 ohms.
I is current in amperes (I'm a bit vague about this one, it's closely related to watts, which you can change if you have a variable wattage battery). This is a measure of how hot your coil will get and so is the important number.
If you do a google image search for 'e-cig volts chart' you'll find lots of pretty coloured charts showing the best wattage to aim for (generally between 4 and 8ish watts) and various combinations of battery voltages and atomiser resistances for achieving that. As you will see, you can either use a low resistance and low voltage or a high resistance and high voltage to achieve pretty much the same result. Variable wattage batteries read the resistance of your atomiser and calculate the correct number of volts to achieve the desired wattage.
Different liquids will have their own 'sweet spot' and everyone will have their own personal preferences as well.
Basic guidelines:
If you're using a standard eGo battery (this will be 3.7V when fully charged) , you'll get more vapour from a 1.8ohm coil. Don't use anything below 1.3 ohms.
If you have a VV battery with any atomiser, crank it up a bit at a time until it starts to taste burnt, then back off a bit. That's the most vapour you'll get from it.
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If none of that makes sense, try
Throat hit depends mostly on PG/VG ratio in the juice (PG for flavour and throat hit, VG for big clouds of vapour). More power (watts) will give you more vapour but not necessarily more throat hit. Nicotine provides a bit of throat hit but not as much as PG.