1. It doesnt matter if its a milli volt or an actual volt because the brain works with itself and lifts its own weight, doesnt matter.
2. You can only lay out chips on a surface, maybe with future technology you're going to be able to create cubic chips but then they would slow down like the brain.
3. Electricity doesnt change speed.
4. Eventually, once the technological brain or biological brain gets too big it doesnt add any more power and even, if not coded correctly, might use the wrong parts of the brain(the outer layers) and slow down.
5. Our brains are gigantic, we've countless amounts of neurons/receptors, its obvious that the outer layer parts of our brains are at their limit and adding more wouldnt be benificial.
6. AI is only good at calculating not at intelect, if you limit energy, it gets stronger. The reason why pc's can calculate so much faster is because thats the sole reason they are build for. A brain that would think and feel would be considerably slower and eventually be just like ours not matter if its biological our technological(but i would guess that biological is better)
Mashallah god has really created us in his picture.