If you keep your expectations in check, I think the X6 m50i will come close to the performance of your 750i.
The center of gravity is higher in the X6, and you can’t totally overcome physics.
I had an X5 with adaptive M suspension and a F01 750i with DHP. The 750i definitely handled better, but the X5 handled very well, especially for such a large vehicle.
If you find the limits of the X6 and your own limits, I think you’d be surprised how great BMW SUVs are.
Driven the velar evoque and full size RR (all rentals) and it’s like driving an X1 and then an X7.
I don’t consider an X1 a true BMW, it’s crappier than a mini, same with Evoque (this was roughly 2019 so maybe they’ve improved since). The velar was okay from a quality feel perspective but with a 4 cyl it felt extremely heavy and wouldn’t move.
The RR was totally unrelated. I don’t recall whether it was a V6 or V8, but I see in an old pic I was at 14.8mpg so assuming V8. Even full of luggage and people the car just moved and obv extremely comfortable.