Harry's GPS Suite Forum

To be able to quickly learn which lines are the fastest, it would be awesome if you could take all of the videos and track data from a weekend, and stitch together the fastest sectors. You'd then be able to watch the fastest way around the track. You'd also be able to see what your theoretical fastest time could be.

On the video side you're right, you can only do a PiP video with the fastest lap as a reference.
Take a look at the details of a single lap of yours. By the lap and sector times you will also find the theoretical best time made up from your best sectors.