Dear Ghayoor,
Normally we’d use the same rotational augmentation correction for all rotational speeds, so, I would normally set the rotor RPM in AirfoilPrep to the rated speed, but you could also look at the sensitivity to speed. The rotational augmentation (3DStall) model applies to a specific airfoil and station, so, the local chord and local nondimensional radial position (r/R) should be used. Min alpha and max alpha should be set such that the CL slope is well calculated (it is best to use a low alpha and high alpha near the ends of the linear region of the CL-alpha curve). You can likely leave Alpha End at 30 degrees, but you could also look at the sensitivity of this parameter; in the end, the accuracy of the rotational augmentation should be assessed (at least by visual inspection).
Best regards,