[RockDriver]

I'm looking at available F15 options in the market, but I could use some clarity on the wheel/tire selection. I need to be able to fit all season run flat tires on if I buy one, so I want to make sure I don't pick one with wrong rims.

All is simple with the standard 255/55 R18 for all wheels choice - there are good tire to choose from. Things get complicated with larger diameter rims.

For instance, by default the 20 inch wheels are staggered with 275/40 R20 front and 315/35 R20 back?

So then the 19 inch set is 255/50 R19 front and 285/45 R19 back, right?

I'm struggling to find all season run flat tires for the 19 and 20 inch sets in staggered format. Would it work if I just put the same size on all 4 wheels, as in 275/40 R20 or 255/50 R19? Any implications on doing this? I know that Xdrive can be sensitive to tire size differences and all that stuff, so I don't want to upset it if I can help it.

Also, in staggered setup, are all the rims the same or do the front and rear pairs differ by width or something else?

EDIT: This tire situation is giving me a headache, because I need to make a decision ASAP. I've considered an alternative of using all season conventional non-runflat tires, but then I'd need the spare wheel. The spare wheel kit is another rabbit hole, because apparently most of them being sold are not quite the right circumference and that could upset the Xdrive.

Appreciate any thoughts on this.