I see lots more cost-cutting corners they could take...

Vapes are probably made in enough quantity to warrant custom silicon. Then the mosfets and charge circuit could be on the same die. It could be mounted COB (black blob).

They could probably use a single 'microphone' (pressure sensor) and determine which setting based on a photodiode.

The PCB's could be replaced with a flex PCB which integrates the heating elements (Vegetable Glycerine boils at 290C, whereas Polyimide can do 400C for a short while). Construction of the whole device can then involve putting the PCB inside the injection moulding machine for the cavities, eliminating all assembly steps, joints and potential leaks, and reducing part count