[330DW]

Hi All,
Been a member on here for years but not a frequent poster. Moved away from BMW last year but got drawn back in again in the form of an F32 420D M Sport.
One of the things I'm noticing on the 4 series compared to my old F31 3 series is that the ride quality isn't that great and I'm looking for some advice and opinions. I know these topics have been discussed at great length on here but I haven't found that much specifically on the F32.

Currently the car is on standard (I assume) passive suspension, 19" wheels with old Bridgestone runflats on the front and brand new Good Year Eagle F1 Runflats on the rear. The slow speed bumpiness I can live with, the issue is on the motorway it just bounces and bumps over any tiny undulation that you can't even see on the road even on pristine motorway that was smooth in my last car. Pretty sure my F31 330D on 100k miles was not this bad (granted X-drive suspension).

I was wondering for advice on any quick wins or changes to improve it. Ultimately I plan on changing the suspension to ACS sports suspension in the near future and been reading all of the reviews and threads on here, anyone on here with the F32 on ACS springs and dampers that can share their experience?
Has anybody changed from 19" RFT to 18" non-RFT and what is the difference in ride quality with the larger sidewall?

Any advice is much appreciated, thanks!