If you have PhotoStory 2013, there is an error in it such that the PIP effects are actually collages. I think this was corrected in 2014,but I'm not sure, as I don't have it.
The image below shows PIP icons in PhotoStory 2013 that are actually collages:
In Movie Edit Pro, PIP in the effects show the correct effects. Selecting an image/video and then selecting one of PIP's causes the image to be resized and placed as shown in the icon. If images/video are superimposed on tracks 1 to 4, you will only see what is on track 4, unless it is made smaller. A PIP effect does exactly this and moves the image to a preset location on the screen. The background will now be what is on track 3. Select the image on track 3, select a different PIP effect to resize the image and location as per the preset. Repeat with the other tracks and you will have a video wall with the video of each playing in its own box.