With modern constant current stepper motor drivers torque is roughly constant up to some speed. Which speed heavily depends on the motor type. Also, doubling voltage doubles the speed range.
You can find some real world measurements in the wiki (search for "torque"). Also keep in mind that there's a maximum RPM of the steppers depending on the printer type, so it makes no sense to optimize for 2000 RPM.
You can find some real world measurements in the wiki (search for "torque"). Also keep in mind that there's a maximum RPM of the steppers depending on the printer type, so it makes no sense to optimize for 2000 RPM.