Everything about this mod screams unsafe. Even the advertising claim of "300W" is misleading at the very least. With the minimum .08ohm build and maximum 4.2V output it can only hit 220.5W, and that's only going to last a puff or two until the battery charge starts dropping..
It's basically a parallel dual battery mech mod using protected Li-ion batteries designed for flashlights with a built in battery charger. You can't adjust the wattage yourself, it works just like any other mech. The only "protection" it has comes from the protected battery and built in battery charger. It's 4.2V max output, just like any other mech mod.
So, you've bought a mech mod with a cheap built-in battery charger and some protected Li-ion batteries. Welcome to 2007. Be aware that the whole reason the vaping world has moved to IMR batteries is because Li-ions can explode and the cheap home-made battery charger in that mod is questionable at best when it comes to safe charging. Personally I wouldn't touch this mod with a 10 foot pole, especially if the batteries were charged.