now that mango is a shield drop master, i'd definitely say him. So much of his gameplay is based around where to be, how to get there, and when to be there, that even if he doesn't pick the "swedish" "optimal" options when he's there, his movement and positioning allow him to play the game the way he wants at his pace.
With that being said, the way leffen is able to ledgedash and such make him pretty darn good. and also, so far, kjh is the only fox i've seen attempt things like shine-lands and laser-lands, which do shave off some important frames in the movement category.
But i'd say mango has the best intentions and heaviest layers within his movement. If you just want to figure out how to get from point A to point B like the best way of getting from top plat to and edgeguarding position near the edge, or covering top plat from the side platforms, then I'd go with leffen.