My question is how do I calculate at what RPM the 5-DRV8825 stepper motor driver can drive the stepper motor?

I have read the TI datasheet for the 5-DRV8825 and it says the maximum step frequency is 250kHz, which I am assuming is for the highest microstepping resolution of 1/32 and a maximum driver output current of 2.5A.

Is there a reference table or simple formula that I can use to determine the maximum step frequency at lower microstepping resolutions and lower driver output currents?

Is the relationship between microstepping and torque linear? From what I understand, microstepping reduces torque?