I have look around for some answers and the ones I have found dont quite work / above my ability (apple motion).
So I want to output a video in lets say a 2:1 or 21:9 aspect ratio. I can either change the aspec in the Project file itself, which seems to mess up both normal and 'title' transitions or I can just add black bars, which works fine for title based transitions (the ones you drop above the clip) if that makes sense, but messes up the normal (between clip) transitions.
I know its possible to change transitions and add aspect ratios in apple motion but I am not sure what I am doing with that programme so it's above my head,
You should not have any issues with the majority of titles and transitions with a Cinemascope aspect ratio. Standard HD video will have black columns on the left and right, though. What specific titles and transitions are you trying to use?