These are the dimension comparisons between an F87, G42 230i RWD and M240i xDrive. Notice the 230i RWD has more headroom both front and rear compared to an xDrive model. Expect the G87 to have the same headroom since it too is RWD. In fact, the G87 may have slightly more headroom since it won't come standard with a sunroof, but that's still TBD. Rear leg and shoulder room however suffer compared to the F87; no getting around that.
Note: BMW has not published the full interior specs of the 2023 M240i RWD model, so I'm assuming it will be the same as the 230i since it's also RWD. The BMW USA site is also inaccurate as it shows the same interior dimensions for the 230i RWD, 230i xDrive, M240i RWD and M240i xDrive. All G42 specs in the chart below are from this official BMW press release.
