No. It would be a logical conundrum for many centuries to study the correlation in handwriting and mind. And the problem in all this is only one - what exactly do we take for a beautiful handwriting, and what for an ugly one?
If we take into account the fact that there is one language in the whole world and it is "inscribed" in our subconscious, then it might make sense to look for the dependence of one on the other, BUT we live in a world where there is a huge the number of languages and even more ways to write them.
If it's just that , for one nation your handwriting will be terrible, and for another - beautiful. It all depends on national and traditional preferences.
It's like speaking one language more beautiful than another: perhaps French is a softer and more drawn-out language than Russian, but it's only you who find melody in French, but not Vasya from entrance 3.
This is all subjective opinion.
Of course, one cannot judge the speed of thinking solely by handwriting. I believe that handwriting, first of all, leaves an imprint on the character of a person. Naturally, a hasty person is quick in writing, and a pedant writes out each letter more accurately. People write illegibly in a hurry and because sometimes the hand does not have time to capture the flow of thoughts. But this is not the only reason for poor handwriting, it also depends on hand motility, psycho-emotional state and other factors.