First part correct Ingo.
Second part as far as I am aware ticking or unticking Display or not allows or disallows just that. Some people don't want to see the photos they would rather have more room on the grid for the aircraft they are picking up.
You can have preferences set to download the photos and have the option whether to display them or not through the Tools menu Show Photo.
I have not tried to confirm, just following logic I suppose as if you have chosen not to download them in the first instance you cannot then chose to display them.
Alan