The Integral gain is a function of the stiffness value. Please check that you have an inertial value set in the Compax3. If it's set as unknown or with a large range of minimum and maximum values, shaft performance will not be stiff. Use the auto inertia detection if need be in the C3 ServoManager's Optimization screen if you don't know the load size. The % values of the gains are relative to the inertial load.
Anti-Windup is always active (if the output is limited the controller sets the integral parts).
With R09-20 you have access to an proportional and integral part weighting factor (Velocity loop I term default 100%; Position loop I term default 0%).
As this affects dynamic performance, if needing more position loop integral gain, set the velocity loop I term to 0 and increase the Position loop I term in 50% increments while iterating through tuning.