1. Yes. It can tell you all sorts of stuff that 3rd party apps cannot and acts as a good sanity check any time you get to a new site. In general, if you can take off using the DJI app you will be able to take off using Map Pilot Pro.
3. It doesn't really matter if you are just using Map Pilot Pro. We have Map Pilot Pro take that image as it feeds into our Maps Made Easy processing for use in adjusting the elevation tags to make them more accurate.