My point is that the Nohadon in that Chapter appeared to be very not-like-Nohadon-at-all. At least in the way it was presented in the visions.
And Nohadon-at-the-end appeared to be very aware of what was currently happening. This is why I do believe that it was likely Adonalsium (or a cognitive shadow of him) that he was talking to. The fact that Nohadon-at-the-end appeared to be aware of Dalinar's godhood, the fact that he recognized HONOR as "young" and "recently sentient" and overall, the language that he used, makes me believe that it was Adonalsium.
The Fourth Shard, I don't think so. But who would have the power to drag Dalinar/Honor into a vision at that very moment? At least an entity of some power, I believe.