I thought you meant that, but just wasn't sure. It's very much similar to that, but each layer is restricted to one single item, so it makes it completely different at the same time. I've seen nothing to suggest it otherwise yet, unless there was new info that came out that I've missed.
Yeah they do. As far as I know, that's how games with a livery editor like this works. The whole image gets compressed into an image when you're racing, that's why you see compression issues with Forza's in game compared to in the editor. File size is not the same though, the reason that happens is to reduce file size.
EDIT: With GTS minimal layers, maybe they wont have to compress images though. That would be a good thing to the small layer count.