The rated voltage of the motor is not the voltage it will be run at.
Most people run the motors at 12V despite them being rated for much less than that.
Some run them at 24V for bit better performance, but they have to use a transformer from 12V battery to 24V.
The lower the voltage the motor is rated for, the better (provided it is low inductance, and sufficient current).
Regarding current, more current is not necessarily good. More current means more heat dissipation.
The lowest current that will do the job is best.
That is why the 0.9A motor is preferred, because it can be run with the LV8729 which almost has no heat dissipation, and therefore no need for a fan in the controller.
Usually people run the stepper drivers at 1/16 or 1/32.
Almost no one runs at 128 or 256, for torque reasons and angle accuracy reasons.
So ignore what the specific driver can go down to regarding microstepping.
Stay with the 4 models I mentioned (2 for low current LV8729 and TMC2130, 2 for higher current S109 and TMC5160).
Ignore all other models, since they are either dated, or have limitations.
If you are autoguiding, then that will take care of any small errors, whether in the gears or elsewhere, so everything works out regardless.