I won't mind seeing digitigrade legs on khajit, but they better not be on argonians. Real lizards don't have digitigrade legs.
They don't have human-like legs either.
But since there's an option for it, I'd say they should have no legs, they should just levitate everywhere, taunting those who wanted levitation in the game. ust kidding. I'd like Khajiit to have digitigrade legs like in Morrowind, with better animations, of course, but that should be obvious, Argonians on the other hand are a bit harder, it doesn't quite make sense for them to have legs like in Morrowind, but it definitely doesn't make sense for their feet to be identical to human feet either. They could use the same animations as other races but they need slightly different structured feet.