All three of them were gods, because they tapped into the Heart of Lorkhan and became divine. And whomever said there are no mortals and gods either had no idea what they were talking about, or didn't put it into context. There are gods, the aedra, daedra lords, Talos, etc, etc.
Whoever said they wren't gods probably meant they were
false gods, in that they claim to be gods, but do not deserve that title. According to the perspective of Ashlanders, the Tribunal are false gods, (Note how they talk about how the Nerevarine will cast down the false gods of the Tribunal.), the Dissident Priests also question the divinity of the Tribunal. Certainly, their divine powers are not their own, they stole them by using Kagrenac's Tools on the hHeart of Lorkhan, and when the enchantments on the Heart are destroyed, they also lose the source of power.
But the Tribunal were all Chimer, since it was after they set themselves up as gods that the Chimer became Dunmer, as to their appearances, I'd guess that with their powers, they can choose how they appear, Almalexia chooses to look like a Chimer, and Vivec is half-and-half, obviously due to all that duality stuff, and it seems like Sotha Sil was going for a Dunmer look, the golden parts seem to be machines, though it may be hard to tell due to poor texture quality.