There were some minor differences with the busbies as you point out: the light cav. busby you speak of is of the elite company (chasseurs and hussars) and the main difference with that of the guard chasseurs is that the funny bag (that is on top of the headgear) faces the opposite side (I think). The plume is also always in the middle/front as opposed to the guard chasseurs who have it on the left side.
In campaign dress the men always removed these decorations and left the busby plain and simple (revell set) or covered with protective oilskin covers.
Since an image is worth a thousand words, I could send you some images of line chasseurs, hussars and guard chasseurs' busbies and dresses. What do you say?