I like to format rather than delete when I start up after downloading anything I want previously.
The supplied card doesn't have space to record more than 3 or 4 flights.
Deleting only the video files is fine for a while but there are other hidden files eventually reduce the available space and might even cause other problems.
Always format in the camera via the app rather than in a computer.
The only reason they mention leaving the "bin in the root"

is so any additional batteries

get their firmware updated.