In the UK, any G3X MSport with an engine greater than 520d has the blue M Sport brakes and has the 664M alloys as standard.
You defo can't have 17" and I'm pretty sure 18" is the smallest size. Look at this thread:
https://g30.bimmerpost.com/forums/sh....php?t=1440456
Poster has dropped from the 19" to 18" with the M Sport brakes. If you want clarification go to any BMW dealer with your VIN, they will tell you what you can/can't have.