KS2
Dimensions - Height-91mm
Dimensions - Width 122.5mm
Dimensions - Depth 72.5mm
Weight- Approx. 678g (Including dedicated battery and 1x SD Memory Card, or equivalent approx 1.5 lbs), approx. 618g (body only)
Sony a7R II
Dimensions - Height 95.7
Dimensions - Width 126.9
Dimensions - Depth 60.3
Weight- 625 g with battery and memory card ( or equivalent roughly 1.4 lbs)
To me there really doesn't appear to be all that much difference in either size nor weight, with the Pentax actually smaller in two of the three dimensions. The KS2 is certainly not something I'd consider a "brick". If anything I think it might be a little
too small IMHO. I sometimes press a rear button unintentionally.
As for the overexposure do you have the camera settings enabled to highlight blown-out areas in the Live View before you take the shot? If not look on the third menu screen >Live View> Highlight Alert.
After 60 years I'm over the "buyer's remorse". There will always be something out there that you think might be better, if not when you first buy it then within a really short time of doing so. I've thoroughly enjoyed my KS2 and the quality of the images have exceeded my initial expectations. Is there something else I could have bought instead and been just as happy with. Maybe. Know what? I don't care. I'm happy with what I have. Second guessing doesn't make me happier.
I suspect once you start shooting with your new Pentax on a regular basis your satisfaction index will go up.