Electric motors do have a constant power region and its ideal to operate there. I would expect teams to modify their transmissions to better fit their motor as more parts of the car are opened up for modification.
If torque is the same at 5k revs vs 10k (to pick numbers from thin air), when you downgear 10k 2:1, you double the effective torque over 5k at 1:1, for the same output revs.
The battery layout and chemistry will limit the actual power that can be delivered to the powertrain (discharge rate). A faster electric car is not one geared higher, but one which converts the most of this energy into motion.