If the chamois feels like diaper while you are on the bike, then the shorts aren't right for you. They shouldn't make your butt look 2 sizes bigger. This is a very individual thing.
I have a couple of cycling skorts, but I generally wear them for rides < 20 miles, errands, lunches, etc. There are a couple of styles; I have found the wrap ones fly up in the front, so the shorts part shows, which is a little weird, because the shorts part look like cycling shorts, but are not as compressive, usually. So, I always feel like my underwear is showing, although it's really shorts showing. I like the ones with the side slits more.