The apron breaking on the CC Niagara is due to the fact, first its brittle diecast, but more importantly it can’t move above horizontal. If the track is uneven or the engine enters a grade the tender comes up and will snap the apron off. The Vision Niagara’s solution was to make the apron thicker rather than change the hinge point which would allow the apron to move above horizontal like most can.
As for the MTH engine you should be able to change the chuff rate with the menu.
Pete