They are different breeds. They are from the same species and a lot of people clump them together. There is the Chinese, Dewlap African and the hatchery African that does not have a dewlap and is between the 2 breeds in size. I'm not an expert, but that is what I have read.
You are pretty much correct. Most of the hatcheries don't have real Chinese or real Africans....they are usually somewhere in the middle. The Chinese should not have a dewlap and should have long thin necks. The Africans have massive thick necks, big bodies and a dewlap. As an example a old Chinese male should weigh 12 lbs and and old African male should weigh at least 22 lbs. Look up Holderread Waterfowl in Corvallis OR on the web to see the differences.
Walt