Ok so to recap what people more experienced than me said here:
Regarding syncing two wheels on the same side, you can:
- sync wheels using tachometer (this is a temporary solution, it will only work for a while and the effectiveness will probably fade)
- sync wheels using a sensor that measures wheel speed in real time. (choose one wheel to be the reference and have the other change so that it is equal)
- use a gearbox that accepts two motors and drives two wheels (this is food for future thought)
Regarding syncing the left wheel set to the right wheel set, you can:
- sync wheels using tachometer (see above)
- sync wheels using a sensor that measures wheel speed in real time. (integrates with the above option, so 4 sensors and a non-negligible amount of coding solves all your problems)
- use a gyro (you should be able to use the size of the X value of the joystick as a base to compare gyro readings and adjust accordingly)
Good luck and don't hesitate to ask for clarification about anything or for more help!
-Leav