The only time I can feel HICAS actually doing anything is just after you turn in to a fast corner, doesn't have to be a sweeper just any fast, wide corner.... just after you brake and turn in, the rear of the car feels like it is just about to snap out on you... after a little while you learn to ignore this 'sensation' and just attack the corner... its just for a fraction of a second that the rear feels a little light... worse thing you can do is correct for the slide you think is about to come...
The whiteline kit is as R33S2 describes and I would be looking at this before you worry about cancelling HICAS...
swaybars, springs/shocks, camber adjustment bushes, pineapples made a HUGE difference to the handling of my car... in comparison HICAS doesn't bother me