I owned 2 E92 M3s and now own a C7 Z51 with MRC. A couple of thoughts/observations...
Was the C7 a Z51? I ask because the base car suspension is very soft. A Z51 with MRC has a suspension that is similar to an E92 M3 in touring mode all the way up to much firmer than an M3 in track mode.
Also, the weight of the steering is adjustable. Track mode is very firm and sport mode is about the same as my E92 M3. Touring mode is way too light for me... I NEVER drive with the steering set to touring (which is default until you reconfigure the car).
With the car to sport mode (steering, MRC suspension, throttle), it is firmer in all respects than my E92 M3. In touring mode, it was, IMO, similar. Without MRC suspension in a base car, many reports are it is too soft. MRC completely eliminates this issue... from comfortable in touring mode to track firm in track mode. I would not buy a C7 that was not Z51 with the MRC suspension. Too soft and not purposeful enough... besides, you get bigger brakes and better sway bars and suspension tuning with Z51. A real no brainer.
IMO, that is one of the issues with modern cars... there are SO many adjustable areas that it is hard to get the car dialed in for how you prefer without extended use. There are so many configurable areas (suspension firmness, throttle response, steering weight, exhaust tone, etc) that you really need to live with a car to figure it out. That makes an hour test drive a difficult thing to have a meaningful comparison with.
Otherwise, your thoughts largely align with my own experience. The car feels like a go kart in many ways. It is incredibly planted and has a TON of grip all of the time. It has so much grip that I worry I'm beyond my own driving ability and not aware of it because the car is making up the difference. The C7 is more of a true sports car than the E92 M3 and once set up correctly, feels more like it all of the time. It also has a ton of torque and power and, as mentioned, insane grip. Any car doing mid 11's in the 1/4 at 120mph (lots of owners have gotten this in real world testing) and over 1G on the skid pad is pretty fun
In an ideal world, I'd have an M3 or M4 for my daily commute and the C7 Z51 for the weekend and track.