The "Clear Cache" item in DJI Fly Settings show that its taking 11.95 GB.  I'd like to delete this, but backup at least some things first.

When I connect my iPhone to my PC using iTunes, I can see a collection of files and folders under "DJI Fly Documents."  The largest of these is an "Original Files" folder which iTunes says is 8.62 GB.  That folder seems to contain all of the photos and videos I've taken so far (I haven't had many opportunities to fly yet).

What other folders from DJI Fly Documents ought I save before clearing the cache?

Download videos and photos, you can clear flight logs if you want, as theses are created after each flight.