few personal opinion comments from my 2019 M550:
20" 668s with non-run flats: I have the Michelins and love the set up and ride. Mind you, I keep a careful look out for potholes. If you tend to hit potholes, stay away from this set up.
I have nappa/multicontour seats (no massage/ventilation): very comfortable.
My previous car was no-frills, so lots of new stuff on this one:
HUD: must have IMHO
soft-close doors: took a week or so to get used to, but now I like it a lot. Only issue is I can no longer close the non-soft close doors on my wife's car properly on the first try, which makes my kids laugh.
leather dash and ceramic controls: like 'em. Both add nice touch. I use the controls (radio, climate control, Idrive knob etc) a lot (I dont speak to my car much, at all) so I can "feel" the difference
After 1 year, no issues at all with leather dash, but I also only park indoors.
I like fineline matte trim a lot, looks good and low maintenence.
Parking plus: good to have the 3D cameras
Dynamic handling package: amazing. try with and without. This refers only to the package on the M5550, other 5ers are not the same. Once you get used to rear wheel steering, you will appreciate it. Active suspension, and changes different modes make a big difference.