Most ebikes use a hybrid tire, so not exactly an MTB tire, but close. Most ebikes use a flat handlebar, without the drops. What's the difference in speed? At 400 watts, the basic online bike computer says 4-5 mph.
I 'drop' to my forearms all the time, on a flat bar. I'm sure you are aware of a few bikes with drop bars. Flat bars seem appropriate for most e-bikers from what I see on the road everyday. I'm passing all but one e-bike, a recumbent. -S