The appropriate value of Kf will depend on your model.
I would generally not recommend neutralizing the damping term. Derivative action has poor numerical properties and is quite susceptible to noise.
The highlighted portion of the transfer function has a derivative-like behavior (Gd = Kd*s) up until Kf. Kf defines the corner frequency for the real-pole that neutralizes the derivative action. Well above Kf one sees Gd = Kd*Kf for a constant gain and zero phase shift.
Setting Kf = 106 results in a -3 dB point at Kf/(2*pi), which will probably have your 1MHz switching frequency interfering in your controls. The actual answer depends on where exactly you would need phase lead in your system and your overall loop response. Furthermore, it may be necessary to add another high-frequency pole, but these are general control design questions and not related specifically to PLECS.