on the rough cheek, i'd say similar to a kimblewick/hanging cheek, dependin ong how tight the curb is - you've got the curb action, but no real way for the poll or curb to come into play, since you don't have any way to make the top bit rotate forwards. so polll and curb would be limited.
then as you go down the slots, you've got more scope for the bit to pivot round the mouthpiece, the top bit to move forwards and the curb and poll action to come into play - so there, similar to a pelham with reins on the bottom ring only, or a plain weymouth with no bridoon.
what i'm not sure about is how the action changes because of the bit down the middle of the main ring that the mouthpiece is on, as opposed to a pelham where the mouthpiece is on one side of the ring...
with all of it, and any curb bit, the relative actions of the curbn and poll pressure depend how tight you have the curb chain. if it's tight, the bit can only rotate forward a little , so limited poll and curb quite soon. if it's loose, the top bit can go a longer way forward (poll pressure) before the curb chain comes into contact.
so how tight you have it would depend on whether you want poll or curb to be the primary extra action.