Hybridization is a very rare phenomenon. What normally happens is 2 fish of different species and from different seas meet at a boundary between those 2 seas. That space can be referred to as a hybrid zone. The fish may choose to reproduce there with a different species because both species realize that neither can properly survive in that area on their own; therefore, they choose to mix their genes to produce an offspring that might be able to. Those offspring don't develop into reproductive individuals though. The hybridizing process prevents them from passing on their genes and that's why populations of hybrids aren't found in the wild.
Angels grow at different rates depending on the species. Having one that's bigger than the other has zero relevance to sexing the individuals in your tank. That could work with conspecifics (same species), but it's extremely unlikely with different species. Unfortunately, it's also very unlikely that you'd be able to hybridized your fish.
Keep in mind that gametes are specific in most cases to a species. Even if your fish lay eggs and the male attempted to fertilize them, the sperm receptors on the egg would not even match the shape of the sperm. It's like a lock and key mechanism. If you put the wrong key into the lock, the lock won't open. Put the wrong sperm shape onto an egg and the eggs and sperm will just die without fertilization occurring.
