We're getting outside of my home hobbyist experience here, but I think you could guarantee the robot would be in a particular position, but the backlash might make it hard to say when the robot will get to the particular position. Using encoders on all the motors would require having inputs for each encoder, which can get complex.
My guess is you can go pretty far with janky parts if you don't run for long periods of time and also measure where they are.
My guess is you can go pretty far with janky parts if you don't run for long periods of time and also measure where they are.