It is a mechanical, it has no set volts or watts or built in safety features.
The battery controls the voltage, it should start off very close to 4.2v freshly charged and discharge to around 3.7 ~ 3.2 then be recharged.
A dvom / multi meter comes in handy to prevent over discharging the battery, measuring coil / head resistance & checking for shorts.
The wattage output is control by the battery's voltage at any given time and the resistance of the coil / head being used.
Example;
4.2v using a 1.8ohm coil = 9.8w & 2.33a,,, as the battery voltage drops so will the watts & amps.
3.5v using the same 1.8 ohm coil = 6.8w & 1.94a