Gearing for 4s and 5s question

If i run a 4s setup in my truggy for racing, and i'am gear 16/46 for an exemple, and i want to switch for 5s for bashing, should i change the pinion or i can keep the 16T without overheat the componant.

If i must go down on pinion, so what's the advantage to run higer voltage????? Just to drop curent??

Because if i go down on pinion when i switch for a 5s setup, the speed and acceleration should be the same, no?????

Need help please on this departement.

Thank you!

David