ok if your use case is mostly flat easy terrain and commuting, id suggest a bafang bbs02 750w. theres also a tongsheng 450w torque motor, idk about it, look up some reviews. bafang is pretty solid and smooth. for 30-40 miles of range on a charge with efficient riding youll want a 52v 17.5-20Ah pack. if you need serious climbing power with your weight and the bike, a bbshd 1000w might suit you better, has plenty of power.