When you use the track motion to create your PIP, you can use keyframes to limit the effect to 1 event. However, since you have an unlimited number of tracks, I find it easier to give each PIP its own track.
It sound like you use the EVENT PAN/CROP tool. When you make your PIP with the TRACK MOTION tool, you can select the 2D GLOW, allowing you to create borders around your PIP.
It is very easy to add a second harddisk to your PC (see the manual of your PC). Dependend on the capacity of the disk and were you live, this will cost you about 100 dollars/euros
Platinum will give you 4 videotracks and 4 audio tracks, which is sufficient for a holliday video.
Vegas 8 pro will give you as many tracks as you like. In addition, vegas 8 pro will give you far more possibilities for making compositions like masking and better tools for color correction. So if you want to make more out of your holliday video, Vegas 8 pro is absolutely worth the extra money, as long as you are willing to invest extra time in learning all the possibilities of Vegas 8 pro.
Ans ofcourse you can make in Vegas 8 pro all the transitions, titles and PIPs you would like to make…..
This job could be done perfectly with After Effects, where you can work with virtual cameras that have the same lens-properties as the lens of the camera that was used in the real shot. In that way you can be sure that all the perspectives are similar as if they were shoot with a real camera. Unfortunately, Vegas has no virtual camera’s.