Well, yes, there is no actual evidence that the Hist created the Argonians, though.
I just can't find any evidence to suggest that Argonians "descended from Ehlnofey" so I'm going to continue to assume that their origin is more alien. Also, the evidence we do have suggests that the Argonians are tied closely to the Hist (i.e., they can sicken from being cut off from the Hist, licking the Hist is part of the passage into advlthood, etc.).
So, at the moment I prefer theories that assume the Hist created/changed the Argonians and that they did not come from the Ehlnofey.
As for the second thing, well there are 2 breeds of Khajiit that look almost completely uncatlike (seems silly to me, especially since they all start off as kittens, but I didn't write the lore), but most breeds of Khajiit are basically various types of cat.
If we are going to stay with the biped versions, I'd rather they keep their posture similar to mer.