I have not see docs on this new feature yet, but the way cropping is supposed to work is that you actually cut off the black bars that are in the video so you do not waste time & space encoding them. The video player on the device will usually add in black borders to fill the frame size properly.

So believe or not if you crop properly you may see not difference at all on the play back. What you gain is smaller size and less video to encode.

I cannot comment on the other features because I have not tried them yet.