I read in another post (I'm trying to find it) it doesn't matter how fast you accelerate as long as you maximize your regen braking.
So basically going from 0-30 in 2 seconds versus 4 seconds as long as you use your regen brakes to get to a complete stop has no effect on Wh/mi? Is that true? I find that hard to believe.
yeah it's nonsense. Sure, the amount of kinetic energy in the car once you reach a certain speed is the same, but getting there expends all sorts of extra energy with higher acceleration (heat from friction, air resistance, losses in the power delivery system etc etc). The equations are complex of course, and a very very slow acceleration isnt the most optimal either, but just slamming on the power is certainly going to eat into your Wh/mi.
Regen is more complex, since the physical motors generate a braking force that is essentially proportional (thought not linearly) to the input torque on the shaft and the electrical load placed across the motor terminals. I'm not sure how Tesla moderate the regen braking, but I would suspect it is via a fast on/off modulation of the load in the inverter, which (if so) should be pretty efficient at most braking strengths.
Basically, the most energy-efficient way to drive any vehicle is at constant medium-to-low speed, with as little changes in speed as possible. For ICE cars the optimal speed is higher, since they waste so much energy in heat, and the time to get to the destination factors in more than with EVs (contrast an EV stuck stationary in traffic compared to an ICE).