If you really want to walk much in ski boots the best thing is going to cost you. You'd want none of those. Instead you'd want AT race boots (also referred to as Rando race boots) like this:http://skimo.co/scarpa-alien-boots?gclid=CPPgzOaiscUCFYOTfgodqoIAhA
rigid sole but highly flexible at the ankle in walk mode, and no duckbill or toe bar to cause issues. But spendy, and you also need tech bindings which also cost.
Now, of the types you mention, your best bet for walking is a leather 3-pin boot. Flexible enough for good walking, thought the duckbill is a pain. The NNN-BC I would skip, because I think you're going to trash that toebar pretty quick.
But, all that said I think I'd get the boots you like to ski in, and carry a pair of trail running shoes for the hiking. The extra weight while you are skiing will be offset by the much greater comfort while you are hiking, IMHO.