I have a 2 ct EC ballerine...yes each setting is made specifically to the stone you pick. And the settings vary slightly depending on the width of the stone you chose...for example wider ECs get only one little diamond in between the bigger ones on the "swoops" and thinner EC's get 2....I think all rounds get 1.
I think anything over a carat looks nice in the setting, it does not get "lost" like it would in a halo, or overly pave setting because the swoops lead your eye to the center stone, it does not overpower the main attraction at all, BUT it does not do anything to make the stone appear bigger than it is. Since the sides match up to the center stones height, you dont get that ratio of a simple band width vs. stone width/height...does that makes sense?
My advice would be try on a premade one in the size closet to the stones you are considering.
Also, another thing to think about (besides the high markup you will pay for a cartier diamond) is you cannot upgrade to a bigger diamond in this setting, you would need to get an entirely new ring for it to look right...