If your intention is to lazy moped it all the way, then you want a lot of battery ah/wh.
Decent batteries are Panasonic cells, so the price for the battery is a fair price.
"vague" is because the more you pedal, the less battery is applied to the motor. Trust me, that's a good thing. A lot of power is needed to move something from rest, so when you pedal to launch, the battery can be used to keep velocity on that flat road.