So I have used Purina and a lot do, it has 19% protein. I use a local duck feed with 20%. So here is the confusing thing, a lot of places recommend lowering protein. I did it once, but I no longer do because I find my flock is healthier overall. Now some will recommend to lower protein with oats, but I don't think that is a good idea. There is a chance they will eat mostly oats and it can lower other potentially important nutrients. There was someone who had this very issue recently. The ducks picked out the oats.
Others are going to swear it will cause angel wing if you keep to high of protein. This is not entirely true. Angel wing is more complicated than that. A lot of what I have read points to genetics mainly be the cause. While high protein can potentially increase the risk with those already genetically predisposed to it. Toxins and malnourishment appear to be a bigger problems and the evidence is not clear. So personally I would not worry about the protein levels.
As for layer feed, you don't have to put ducks on layer feed. You can give them oyster shells on the side when they start to lay. This is what most people do and it is more recommended.
I've seen pictures, but still don't know the breed
