In general FP designs all his watches with a 'thick' bezel. This is why the models offered in only one size all have the thick bezel look (CS, CB, CT, TN, UTC, etc). For watches that come in two sizes (40, 42), his default design is always for the size 42 - hence the thick bezel. That's why all the size 40 models with a 42 option will have a thin bezel. Basically the 42 is the "correct" design, while the 40 is the "secondary" design with a thin bezel.
You cannot compare the bezel size of a 40mm watch that only comes in 40mm vs. a 40mm watch that also comes in a 42. It's more an aesthetic thing than a direct size to bezel comparison.
As what Christian stated, the dial size are exactly the same. The one thing that is slightly different is on the movement side. The 42 will show slightly more of the movement than the 40. Not so noticeable on Octa models, but the new RQ is somewhat noticeable. Perhaps the CO as well but not sure.
In regards to the CO winding - mine starts with less resistance and increases tension when closer to full wind.
Hope this helps!