The protank mini 3 would get hot since it has less area to conduct/spread out the heat. But the head of the vamo should NOT get so hot that it's uncomfortable to touch. Warm, yes, but not hot to the point that it gets uncomfortable to touch.
But then,
1) what is the resistance of your topper?
2) what's the voltage or wattage you set the vamo to
3) how long will you press the fire button and the intervals between firing.