I have a similar problem as well as the difference in pixels. When I import an ARW file from my Sony RX-100 -V camera and use Serif Lab's lensc corection, the image is slightly distorted compared to the jpeg image imported from the same camera. Straight vertical lines are curved. Its very easy to see on buildings. Exactly he same happens if I choose "no lens correction"
However, if I use Apple (core image raw), the image is correct.
(Images are in the first post in this other thread )