Well, they're certainly not marred by sin, original or otherwise - I don't know what else one would call it.

seem to be the same thing or different aspects of the same thing, in Lewis's worldview

Yes - hence the point made somewhere by "Lewis" (the narrator) - but I think it's in Perelandra that in practice, how on earth would you tell the difference between an angel and the sort of super-powerful, intelligent non-corporeal aliens of a certain sort of science fiction....