The library manages the motor functions using the MD_Stepper library (https://github.com/MajicDesigns/MD_Stepper or the Arduino library manager), so any controllers supported by that library can be used.

MD_SmartCar2 was developed using inexpensive 28BYJ-48 stepper motors (12V version) bundled with a ULN2003 'stepper driver' board (high voltage, high current darlington transistor IC) that need 4 digital I/O pins to drive the motor (shown below).