Take photo only on interval without waypoints

The mission you shared has actually a 50x40m grid/mash, not 40x40m.
It will take a photo every 40m because you have set a Photo Capture Interval of 40m.

The Mavic Pro has a FOV of 78.8° diagonal.
This results in a vertical FOV of 52.5° or 78.9m at 80m high,
and a horizontal FOV of 66.6° or 105.1m at 80m high.
Your grid is based on a 50% overlap.

The DJI drone with the biggest FOV is the Phantom 3 Pro (94° diagonal).
The next best upgrade would be the Air 2 S (88° diagonal).
The vertical FOV difference of the Air 2 S compared to the Mavic Pro at a hight of 80m is only 13.8m, NOT 20m.

When using your shared mission with an Air 2 S you could increase the Photo Capture Interval from 40m to 47m to keep the 50% overlap (92.7m/2=46.5m or 40m+13.8m/2=46.9m).

Also have a look at this thread: