Most of that question is dependant on the THC you pick . You can easily get steps of .001 with a stepper and 5mm pitch leadscrew. 200 steps / 5 = 1000 steps per inch (not counting microstepping) You can get well over 100 IPM vertical motion IF your THC will handle that speed in the feedback loop. The other issue is the resolution of the THC . .002 change in height is only about ,2 volts change A lot of inexpensive THC's cannot hit more than 20 to 30 IPM without serious overshoot problems so having a fast servo is not going to help much.