You can actually just use the Pix4D app and upload the pictures to us! We didn't see the purpose in redoing a perfectly fine app... We have some stuff coming up soon that will make data collection a lot more automated, but for now you can just use that app and it will work just fine.
The DJI cameras do not record sufficient precision in the geotags to be useful for georeferencing. They give the position in degrees, minutes and whole seconds with no decimals. We require at least three decimal places of seconds precision to be able to use the exif geotags. We have asked DJI to address this in firmware with only minimal interest on their side. We haven't been able to figure out why they don't expose more...
Other cheaper cameras do this as well, so it isn't just DJI.
Always always always use the narrow field of view, low resolution setting to limit the amount of barrel distortion. People have had a lot of success flying at 125 ft, 8 mph, and taking images every 3 seconds.
Make the pixels you upload count. Large resolution is less important than good resolution. On the Vision camera, as with GoPros, the center part of the native image is pretty good but drops off quickly as you move towards the edges. Keep this in mind while planning your overlap.
It is very possible to create really good looking maps with the Vision+.