Don't assume that MY will be planted like your MX. I love the way the MX drives, it would be my favorite Tesla if it did not have the idiotic doors and front windshield. In fact, when I was buying my MS, the MX was exactly the same price and would have been a MUCH better fit for my family. But alas, I cannot change the way the world works. When I test drove a SR+ Model 3 recently, I did not like the way it felt at all. It felt extremely scary at high speed on wet/cold pavement, very unstable on the same road where my MS felt like it was on rails driving in the same conditions. The steering was extremely heavy and nervous, even on its lightest setting. The ride was absolutely unacceptable, with a weird bucking motion and very rough. It was very, very noisy -- even at low speed where I could clearly hear the new pedestrian warning noise. On the highway the noise was at the level of a non-premium car or worse. I loved the interior and the seats, both front and back. It really fit me like a glove up front -- so much better than my MS, which has terrible seats in comparison. The seating position in the back was so much better than the MS! But compared to MS/MX the M3 is very, very different. Reading all the new reviews of Model Y that have been popping up, it sounds like MY handling, steering, interior noise and ride quality are substantially similar to Model 3 (or worse.) So don't assume you will like it compared to your BMWs and certainly to your MX. Both my Model S and all of my BMWs (still own a 550i) and Mercedes felt way, way better than the Model 3 in terms of steering (way steadier, better feel,) ride (WAY more buttoned down and stable,) interior noise (no comparison, M3 is extremely loud) and overall driving feel.
Before you say anything about the 18" Michelin Primacy MXM4s -- they are my favorite tires. I have been putting them on all my cars ever since they came out. So this comparison has tires constant -- all my cars are equipped with exactly the same Michelin Primacy MXM4s, as was the Model 3 I test drove.