I don't know about Angorians, but I don't see any reason why Argonians should. They're pretty much aquatic reptilian humanoids, maybe make them more clumsy on land, but at most they should just hunch over and drag across, like some sort of slimy amphibian.
Khajiits, maybe. Depends on which breed we get.
Why ? DO you know many bipedal amphibian ? All amphibian i know are fishy like or quadruped.
I think it would be an awesome idea, sneaking is about hiding and move stealthily, dont we double ourselves when we try to sneak to avoid to be at eye lvl ?
And about the Lore, as there are many sides of it, it wouldn t hurt that some would go on 4 and some not.
Althought i see kajhit in gelid skyrim, i don t see the cold blooded Argonian liking it at all.