Also, TTS Device does a good job with them, especially Vect. That dude is the most delightfully evil sadist in actual lore, and him humoring his enemies right before he twists the knife is how he loves to operate. For example, a human slave he recently captured is taken to his chambers. Vect offers him tea, which he accepts because he has no real choice otherwise, and listens as Vect tells him about the events of the Fall. Why does Vect do this? Well, its a nice story that he loves to tell, and most humans haven't heard it. Also, the tea is indigestible by humans, so soon after Vect finishes the very abridged version, the poor sap gets the worst stomach cramps ever as they drag him back to the slave pens before his torture session can begin.
For Craftworlders, Saim-Hann really play up the Celtic aspect of the Eldar, with lots of clan rivalries and a complete disdain for sanity, and even "woad" paint on their armor and vehicles. Yes, GW hypes them up, but that's because its pretty easy to make them Your Dudes thanks how individualistic they are. Altansar are nice if you want something more disciplined that aren't the stereotypical pricks of Biel-Tan, with lots of Dark Reapers and a Phoenix Lord who went "Fuck this shit" when his brethren were making fancy knives and decided the best way to kill some fuckers was with a big-ass gun.