Here's some pics of the '21 X5M with 20" square winter wheel setup. If anyone was wondering there is just enough clearance for the brake calipers. Probably about 1 inch gap.
I originally bought them on getbmwparts earlier this past fall for the '20 X7 and the 4 wheel set was roughly $4400-4600 with tax and shipping from the east coast to San Diego. The reason I did not go with staggered set up or just replace the tires only was 1.) convenience of just swapping out the wheel sets at the local tire center for $40 and maybe a 20 min wait.
But also, 2.) if it actually snows heavily in the So Cal mountains, Cal Trans and CHP requires everyone to have chains or cables and Peerless makes a snow cable that fits 275/45R20 and it only costs about $98, so I usually will by 2 sets and put them on all 4 wheels.
And yes, even though technically it is only required that we put chains on the rear wheels only, there are areas on Hwy 38 going up to Big Bear from Yucaipa where there can be numerous areas of black ice and snow drifts that come in sideways when conditions are bad. So better safe than sorry for an extra $100 for a set of snow cables.
Sorry for the crappy cellphone quality it's been a long time since I posted to any car forum. Also a photo of the same wheels on my '20 X7 (the winter tires and wheels work great in sandy high desert sand like in Barstow!) and random '21 Sierra pic and '20 M2C which will pretty much be collecting dust this winter.
Ironically the Sierra is rolling on 20's also but the square setup for it is 275/60R20" so a tad bit taller than the BMW's 275/45R20.