You can never go wrong with the Coolfire range of products.
These all have internal batteries for longer lasting, fast charging devices.
The Coolfire Ultra manages to cram a massive 4000mAh battery that is capable of 150w!
This kind of performance is usually reserved for much larger dual 18650 battery devices.
Innokin also have some of the simplest devices to use, you set your power level and it wont accidentally change from being in your pocket and taste disgusting the next time you vape it, you simple hold + or - and then you can adjust your power levels, simple.