Gaming

And here's what I get from all the different render modes...

 
 
 
 

It only looks smooth in that basic shaded mode and once you get to using Eevee everything starts to look almost reflective and angular. And this time I noticed that this particular head does have a little seam at the back where the vertices are not merged. Don't know if that's common with all models or just this one.

Well, as long as the end result when exported looks the same or better than it did when imported, I don't really care about the various renderings... And I see "double" vertices along seams on pretty much everything. Probably for easy of texturemapping? At least that's what I assumed....

What do you mean by double verts? 

Two vertices in the exact same spot....

That's probably why it looks like it does then.

EDIT -I believe Blender has a mesh cleanup function, I would try running that and see if it fixes the problem.

which one of the problems are we discussing now? The seams with double vertices has never been an issue... (And they're not what makes the shading look off... at least not in the files I've fiddled with - I think maybe it does in some of the clothing nifs, or rather it might be that the vertices are NOT double in some places that causes weird shading on some skirts....)

Double vertices is definitely a problem within Blender and should be avoided if you want the shading to work properly. Whether it's a problem in the Skyrim game engine is a different question. In fact it's possible that it may be an issue created by the nif import script.
Are the vertices still doubled in NifSkope?

Haven't checked. I haven't noticed any issues, except it's a nuisance when you have to move them and need to get both selected....

I've managed to solve my not-smooth shading thing with the face...

 

That previous weird effect was a consequence of not having the correct Normal map plugged into the right node. I still can't find the normal/specular texture for the eyes so I suspect that's just using one from the vanilla game so that still looks a little off but the skin looks a lot better now although I'm guessing a bit at the subsurface value.