The upper arm will get leaner through isometric exercise. Put a couple of soup cans next to your living room chair. Use them as weights and lift them over your head, out to the side. There are exercises on the internet that you can do too. Then remember, some of us are just going to have some saggy upper arms because of our genes. My mother is only 104 pounds but her arms are floppy. I'm fat, but my arms aren't.
C-section flaps I don't understand. I had 2 c-sections, but I don't have any flaps. Of course, my scar goes vertically instead of horizontal. That might make a difference. If you have strong muscles underneath your tummy, I suggest using a tummy control panti to help with the excess.