I think it's going to be a really long time before we see any movement towards Android P. Many many months IMOMy phone is not unlocked. The UI in Nougat and Oreo are very much the same. There are some features that are different to each one.
I don't see how you can upgrade to Android P. Oreo for Samsung was just released back in March. Unless there's something I don't know, P won't be released for this phone for quite a while. But I hope I'm wrong about that.