You are right I would change it to the setup,
I am using some motors from China, they are 24V, 250W, here is mor information about the their specs https://www.ebikethaikit.com/uploads/443/files/MY1016Z250W.pdf
For the 24V supplied I am using two 12V lead-acid batteries of 12Amph in series and to supplied the arduino and the logic part of the driver I am using a regulator to get 5V from the batteries, the motors are not the problem because I switched them and the one the was moving faster now start moving slower and vice versa, I am using a variable for the speed to control de PMW values because later on that value will be given by a joystick maping the values from the joystick to PWM values, here is a simple sketch of the conection I have and a picture of the motors I am using
