Ooof, Just watched your videos - you've receive good advice so far.

One point from me which I don't think is covered from what I've skim-read - please don't connect/disconect steppers with the drivers powered/active. Being an inductive load, and that the stepper windings are under constant excitation you will generate high-voltage spikes on supply interruption to the stepper that can damage your drivers. Not much of an issue if you're replacing that kit, but useful to get into a habit of powering down. The problem gets bigger as the steppers (and drive currents) get bigger.