Your point of view is understable, yet I suggest you to read the Dark Eldar trilogy of Andy Chambers (especially the last novels, which involves the mandrakes and their sub-realm, Aelindrach) to help you enjoy the new mandrakes as they now truly are: something that is no longer eldar, even for the other citizens of Commoragh.
"Bawww, the old Dark Eldar don't understand me!!1" Seriously, the new models look like combined wet dream of a thousand underaged Naruto fanboys with a bit of Shadow Fanart from Sonic the Hedgehog mixed in for good measure and lovingly selected works from Linkin Park and Bullet for my Valentine playing in the background. The aesthetics of the old SM (no, not that kind of SM)-Mandrakes is debatable, but I always liked how they, together with the Haemonculi, were the really ugly part of the Dark Eldar (with other miniatures already being unlikely to become runner-ups in a beauty contest).
I don't know much about the old Dark Eldar so I won't make an attempt to say they were better/worse than the new ones; and I don't care either if the new mandrakes look like Illidan Stormrage or whatever: their new aesthetic clearly defines them as the inhabitants of Aelindrach, which is fine to me. About the lore, I actually like the idea of the mandrakes getting their own sub-realm instead of being bound to the haemonculi covens, it just makes Commoragh appear even vaster and shattered through the Webway in more or less independant regions.
Mandrakes are really one of those things that can't be much discussed other than theory. They do resemble eldar, but as far as are they eldar, were they eldar, will they be eldar etc. is quite different. And yeah, I think the previous edition mandrakes had a little different looks, but otherwise they are supposed to be "creatures of shadow".
I feel responsible for this entire discussion in some way... Getting back to the original point, I think it was mentioned, but I was reading Xenology from Black Library and it makes various mentions of the Eldar be externally similar to humans, so I think we're going for option... 3 based off of that.
According to the lore the Eldar are both obviously alien and able to pass as human. I suggest restricting their skin colour to shades of white; not as in "caucasian white people"-white, but a white that would make them look unnatural to a human: snow-white, marble-white, white as polished ivory, pale as death. This is similar to the Salamander Space Marine Chapter; where they are blacker than "black", the Eldar would be whiter than "white". Together with pointy ears, cat-like eyes and alien movements this would be sufficient to mark them as decidedly non-human regardless of their facial features, which could range from "pretty human" to "uncanny valley" depending on the player.
They are a more white tone than humans almost to a marble white. When you see people painting their Eldar with human or elf flesh tones its people who do not know the lore of the race or just pick up the paint that is called Elf Flesh that GW puts out cause its simple to do. The only ones who are whiter than Eldar would be Dark Eldar as the lack of a real sun would cause them to even be a ghostly pale white. There is more white in my avatars fleshtone then there is a pinkish color but my blonde hair hides how white the face is.
Well it does say in the codex that they closely resemble humans, but n their minds specifically they are most alien. I don't disagree with you, I actually picked option 2 for flavor-sake, but its not a crazy thing to think Eldar would appear rather human with an alien elegance in their walk and eeriness in their words.
Plus anyone who looks at your avatar will probably gaze down at the magnificent fun balloons and not really worry too much about the skin colour.
I voted "Something in between" I'm a big fan of Beckjann's art. They definitely don't look human but aren't unattractive either. Just creepy enough for me. For obvious reasons Crafworld Eldar would be slightly less creepy looking.
