Does the 4.4.1 update improve 3rd-party camera apps or are the enhancements just to the stock camera app?
Updates of this kind are usually for the camera as a whole and not just app centered. For a detailed analysis I suggest you read this. The update as a whole brought changes to the API the way the auto focus, White balance, etc in pictures taken as a whole. You will notice changes(for the better) in pictures taken from a 3rd party app too.