changing to non approved tyres (without star mark) can void a warranty. For example.
You fit a non runflat on a runflat only wheel. You blow out. Your fault.
You fit a non runflat on a runflat only wheel and experience tyre pressure loss problems. Car is within warrenty , TPsensors are defect say BMW , and the tyres fitted are to blame. You must pay for new TPsensors and new tyres.. no warrenty. Its quite simple
Changing the wheels to non spec items can also void you suspension, as wider track tyres "can" increase the forces applied to the front wishbones, voiding the warranty there ..
As would lowering the car on non OE springs. A damper would not be covered in that case either.
With regards to tyre dimension or rolling diameter, the speed sensor takes that into adjustment. As long as the dimensions are equal on both sides, the speed is equal, even if its inaccurate.
Get it on the GT1 tester at an independant, and get an honest diagnosis
Been there, done that, wanna do it again