[Number 3]

Part of what the OP is experiencing is a level of body rigidity that the Germans have mastered.

Historically, and GM has improved significantly with the ATS, GM has had less body rigidity that has had to been made up for with a very stiff chassis. The Germans (BMW for example) have had more stiff bodies that did not require the chassis stiffness or tire stiffness for that matter. This made for some differences in how the cars rode.

There is a reason why German cars have always had that chassis "thump" that feels so much more solid than American cars.

That being said, with Alpha you see what GM can do in this regard.