Some NFEs are, or have been, UU, such as Chansey, Scyther, Porygon 2 and Magneton. All the other NFEs are NU, in reality.There is no way that Pokabu will be in UU or NU.
It's NFE.
If NU is the lowest usage tier that Smogon gets to in generation 5 (which I really hope it isn't), then Pokabu will be at least NU.
NFE *should* mean nothing in terms of competitive battles. It's just an in-game status of a Pokemon. It's a label that Game Freak give to certain Pokemon, just like "legendary", or "starter". It's like how people say things such as "Articuno and Regice should be OU, because they're legendary". It's just a completely flawed arguement.
It does happen that most NFEs have poorer stats, and are almost completely outclassed by their evolutions, so it's unlikely one will ever be OU (although Porygon 2 almost was in DPP), but you can't say it won't be, just because it's NFE.