It depends on the ohm rating if the coil. Google vaping chart and you'll find a chart telling you what voltage to use for what ohms of the coil (I'm on my phone otherwise I would put it here for you)
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So i normally vape at a voltage of 4.2 so I should go for one with 2.2 ohms but if I buy one with say 1.8 resistance and vap at like 3.7 what's the difference?