I have a front hub from a Swytch ebike kit that I use with a 48v 20a controller and battery. It is rated for 260RPM's at 36v, but running at 48v makes it a 328rpm motor. That is the sweet spot in my opinion of weight power and speed. I can go 25mph on flats, and 28+ downhill, which is perfect for NYC. This allows me to keep up with the cars in the street and run with the timed lights. Been running this setup for over a year now without an issue.
It's hard to find a rear AKM-100sx with a 260rpm at 36v. The rear 100sx motors all seem to be either 201rpm's or 328rpm's. When boosting to 48v you will either barely go 20mph or will not have enough torque to go up a hill. Make sure to look for a 260RPM
@36v rear motor if your planning on powering it with 48v. Or get a straight 328rpm @ 48v motor, but I imagine they are heavier.