So I was at gamescom yesterday - and I did get to play about in CAS.
The bad news - CAS is totally not finished. There were a couple of things in the UI that were visible but not available to choose - the tooltip was "coming soon".
I saw the options for 5 ages, "coming soon" and for traits - also coming soon.
The sliders for fitness and bodyshape work pretty much as Sims3.
The mouse clicks need to be set to slow to have the most control over the "tactile" sliders. I was able to make a sim female with enormous breasts and then jiggle them up and down in CAS. I digress. Depending on the area you choose you have a bigger area to drag, so a large butt is possible, but ludicrously fat calves are not - the sims do keep some proportion.
I think it will take some getting used to, but a GOOD sim maker would probably find the detail mode useful. In detail mode the sims face fills the screen and you can push and pull the areas on the screen. It is possible to move the lower eyelid etc.
Clothing - there are color ways but they look fixed - I did not see a + sign to add more colorways, but I can hope that is coming soon. At the time i played with it, you got a sort of swatch from a drop button and applied that swatch to the sims clothing.
Ask me for more info if you like, I am not a very good reporter.
The site don't jive? PRESS F5