The main difference apart from the size/capacity (17L compared to 28L) is the fact that the Mini Backpack has a top opening only and does not pack flat. With the smaller capacity, we felt that this was not needed. The laptop sleeve is accessible from the side.
Yes, absolutely. Simply unzip the expandable front sleeve and unclip the buckle to put your shoes in. This front expandable compartment is actually the same size as the one on the Backpack II.