The appearance doesn't really mean many things. What we see is a modified model, and the factory that made the model may not have received a real blueprint.They're all new, given that all of these have never been seen before, bar the YJ-20 (which was formerly called YJ-21 for the last few years). The YJ-15 is new, the YJ-17 is new (and while it does have the "17" designation, its HGV looks different and a little flatter than the DF-17 and is, of course, a ship-launched HGV that did not exist before), the YJ-19 is new, and the YJ-20 has been in service, just known as the YJ-21. So 3/4.