(with the exception of the ever kinky Vivec)
Vivec wasn't the exception. I think it's implied somewhere that Almalexia's Hands play with more than their swords, and Ayem herself is depicted as a fairly sultry girl in the game. In the Sermons, Sotha Sil divides himself so he can have six with Ayem. They were all envisioned as sixual beings, at least by their original creator.
To answer the question, I really wouldn't know, having never really inquired into, or been given the opportunity to indulge in, any sixual encounters. Partly because they're xenophobes and probably aren't interested in me. Partly because only the main characters tend to be very well realised anyway, giving little opportunity for romance (though the khajiit girl one was a nice surprise). And party because the new family friendly direction Bethesda have taken, meaning sixual content tends to be well hidden. I really don't recall any outright signs of sixual repression either, except the bowdlerising of the Real Barenziah, which I think is just the aforementioned family friend direction again, but, by the same taken, lust is not incompatible with sixual repression.
But with a society with a fairly daedric bent, glorifying in assassination,violence and savagery, and adoring a divine, over-sixed hermaphrodite, "irrationally comfortable" with the idea he might have killed a beloved national hero... prudish doesn't seem quite appropriate.
Edit: I'll add that the UESP normally isn't a reliable source, but this piece of trivia thankfully has a couple sources. First is the Daggerfall joke book, which characterises Dark Elves as lustful. Second is the Real Barenziah, which, interestingly, claims young elves
in general are promiscuous, and makes no distinction as to race.