Help: Feel difference of Stiff Springs/OEM Bar v. Thick Bar/Softer Springs

So I had my Z4 tuned well at the end of last year's autocross season as follows: H&R sway bar at mid front and rear, 550 front springs / 700 rear springs.

Because I am a tool, I wanted to experiment and see if I could get more grip by going back to the OEM sway bars since I was at mid front and rear on the H&R bar, which is 2mm thicker front and rear than the OEM bars.

I swapped back to the OEM sways, and the front was fine (not a significant change), but the rear was wallowing a lot. So I figured that the rear H&R sway had previously been contributing more at the mid setting than the front was at the mid setting.

As a result, I upped the rear spring from 700 to 800. Now, the car feels balanced, does not wallow, but the overall car feels just different. It is less solid feeling, but there is no more or less body roll than when I had my "perfect" setup from the end of last season. I think I probably have a little more grip now, but the feel is the main issue that I am seeking feedback on.

Is is because the sway bar is a fixed piece of metal that it provides a more rigid and inflexible feel in its approach to reducing body roll whereas the springs are innately more sloppy?

I really like the idea of decoupling the suspension through springs and the OEM bar rather than losing independence to some degree via thicker sway bars.

Comments?

By the way, I cannot get the H&R rear bar to the softest rear setting, otherwise I would have set it there.

The difference between the two can be analogized as like the difference between a tire with full tread (like the softer sway and stiffer spring) and a tire with nearly no tread (like my stiffer sway and softer spring setup). That's the feel difference I am trying to reconcile.