The job of delivery services today is delivering small packages, not information. So everybody (USPS, UPS, Amazon) is converging on the same feature set:

- Van big enough to stand up in

- Door between driver compartment and package storage

- Bin/shelf type package storage, not bags or piles

- Good visibility

- Battery electric

- Optimized for 0 to 30 MPH with lots of stops. Aerodynamics don't matter much. Regenerative braking does.

Amazon has some cute features. The driver wears some small RFID device, and when they step out of the truck, the door to package storage closes and locks, and the truck won't move. Amazon's new vans also have very high visibility from the rear, with many LEDs, so it's hard to rear-end them by accident. Good because they double-part frequently.