Do the rules differ in any real way, or are they just goofy little
regulatory differences that have no immediate impact on most real
flights. (For example, if Belgium's VFR cloud restrictions are
different than France's, it's just a "gotcha" on a test, rather than
anything "real".)

Jay, this =would be= something real. The point of VFR cloud
restrictions is to give IFR traffic a chance to see you when they pop
out, and you them. If you are where they don't expect you, this is as
real as coming straight in NORDO to an uncontrolled field - a pet peeve
of yours.

Right, poor choice of words on my part.
I guess I mean to say "flight critical" -- not "real"...

Jay, I can give you "the little french girl's" email address.
She rented a plane and instructor for a couple hours last year, flying
around the area of France she grew up in. She could add to what others
have posted.