Been curious for a while. There are certainly some differences in the details, but at surface there seem to be parallel to me between Eldar and Vulcans, Dark Eldar and Romulans.
They're both basically analogues to light/dark elves, but additionally there's the psychic connection, the depth of feels and suppression of same by the "light" version, embracing violence and slavery by the "dark" version, and so on.
Obviously the 40k versions are somewhat more extreme in a lot of ways, but 40k tends to lay on tropes like a hammer in any case, making anything a more extreme version of the source material.
I guess I'm looking for any evidence for or against the idea that the 40k designers drew inspiration from Trek, whether in notes, interviews, blog posts, etc.