My experience is that - to use the 2 Amp feature, you must use the included wall wart (5.5 V - 2 Amp).
This because I don't have, nor I've been able to source - an USB charger to BC 1.2 spec.
Therefore, with micro USB power supply, I have been able to use 1 Amp charge only.
The charge current start at 2 Amp with a discharged (< 3.7 V) battery, and decrease to 0.5 A when voltage reaches 4.2 V, then it starts a very peculiar (quick pulses) battery charge maintenance mode.
The charger totally follows Li-Ion charge protocol (CC / CV) and has very high precision - with a 5 digit (!) voltmeter, the precision seems to be 0.1 %, which is kind of outworldish. Of course with a sample of one - it could just be fortuitous.
In the end, the charger charge the battery and keep it topped to max. It does it way better than other charger I've seen, stays cool all the time, so it should last for a while. Also, it is fully protected against short circuit, as when you install the mod backwards in the charger.
I believe the overall charge performance is slightly diminished by the PTC in series with the battery, inside the mod.
But that protective function is essential, as the charge port would be literally destroyed if the device's positive contact is accidentally shorted to ground.
As it is, in case of a short of the device's charge port, there is a weak but visible spark, and that's all. Safety first.
In few words. It is much more than a standard charger, you buy it because you like it, not because you need it. Just like with the device itself.