We've had a Cooper from new - went petrol over diesel and it regularly averages 50mpg, though its a 3 door hatch not the Clubman. I've experienced the same petrol engine in a 1 and a 2 Series and found it quite a bit more thirsty, so not sure how it would perform in the Clubman. I have driven the Cooper D as well and whilst it was quite refined for a small diesel.
Options wise the interior looks much nicer with the larger navigation screen and I also found the head up display was essential because the standard digital display in the speedometer is poor and very small and won't display things like navigation instructions - the head up display fixes this. Didn't bother with the stereo and never found it an issue. I have the upgraded system in my 5 Series so it's not like I don't have anything to compare it with. I can't remember if they are standard on the 2019 Clubman or not but the LED headlights are essential.
We've had it 4 years now and it's been cheap to run, efficient and 100% reliable. A really great car.