I am five six, and 213lbs with a smallish waist. A large worked well for me. I probably could have gone with a medium for a fit and flare look that actually fit my hips waist (except I'm quite busty - 38F - and the large fit the girls perfectly). The large did come in in the waist but I still need to take it in a tad to really make it flattering to my curves.
The fabric feels great and the color is deep, true, and rich. It's also see through  held up but i don't think people well be able to see your unmentionables as long as they are a color close to your skin tone. Best yet, the fabric does not hightlight my lumps and bumps (a HUGE concern for me) but I'll still use a lite control short for security=vanity.
Comes just two inches above my knees which means my big butt and upper anf mid-thighs are still nicely covered while still allowing me to show a bit legs without sacrificing class