From my experience I would say that the ken uses #2, #3, #4 and sometimes #1, but #1 usually isn't very viable with someone that is really good with the ken. Furthermore, and by now you know this is coming, I would say the same is true for taijutsu.
I think we're working off different definitions of "internal skill", and I think that might be contributing to some confusion. I'm talking about the ki/kokyu skills Mike Sigman and Dan Harden like to discuss. I don't see how one can blend/flow internally the way I tried describing in #4 with a sword. It requires direct, physical contact.
I also think it's interesting that you don't think flowing/blending with momentum (#1) is viable or used much. Wouldn't something like, say, ukenagashi be considered flowing/blending with momentum?