I seriously considered the M6 before pulling the trigger on my 650i, and like you I felt that the M6 was simply too much car for me.
I didn't need the extra HP/torque, since the ponies in the 650 are probably more than I'll ever really need, or use. And while I would've preferred the DCT over the 8sp, unless I was tracking the car, I don't think I would've ever really maximized the DCT -- and who really tracks an M6???
Don't have Adaptive Drive, so cannot comment on it. But like you I think the ride on the F12 is just right, and given the different modes (Sport+ to Comfort+) it fits my lifestyle just fine. It gives me the best of both worlds.
And, now, if I want to relive my track days, I can probably use the 20k that I saved from not buying the M6 on a used spec Miata ...
Never liked convertibles, so the F13 was never a consideration.
So, to answer your questions, yes, the 650 makes me very very happy. I now have this annoying habit of turning back and looking at the car every time I park her ... just to get one more glance at its sensual lines.
(And if you want to go for the SM Blue, go for it.)