I am new to ebikes and would like recommendations of a purchase. I am shopping for a compact or folding bike (20" wheels, less than 55 pounds total) to be used as a commuter on hills in San Francisco and Berkeley. My max budget is around $2000. Is a 250 watt mid-drive powerful enough for throttle-only for steep grade uphill? Is a 350 watt rear-hub an viable choice? The primary rider of this bike is a 5' 4" woman, 140 lbs, average leisure cycler. Thanks for your time and consideration!