yeah watt is volt * amps
if volts are higher then the device was made for it will kill it
amps according to owns law are drawn not pushed amp = volt / resistance
devices which does not control how much amps their charging system draw are lillegal and dangerous in most countries
the more power is drawn from a charger the lower level volts it can deliver so making a charging system get even close to the max the charger can deliver is a bad idea as that would lower the volt level and in the end make the charging stop