The footings layer defines the area the data will cover, coordinate grid system and spatial precision. Establishing the footings layer makes life easier because all data will end up compatible. It will require some processing when the data is downloaded but worth the effort in the long run.
My favorite for agricultural work:
Area covered or extent should be 2X what you think you need.
Coordinate grid system is Universal Transverse Mercator (UTM) and meters.
Precision is 3 meters or 10 feet.
Your favorite should be based on what you would like to measure and the accuracy needed for the results to be useful.