One of the things that interests me about Wangxian's sex life is that in reality Lan Wangji must be soooooooo gentle with him.
Hear me out. There's this very popular and widely accepted idea that everything in literature is about sex but sex. I... don't really agree that everything in literature is about sex, but I do agree that sex is rarely about sex.
Yes, Wei Wuxian likes getting tossed around and bitten to hell etc etc and Lan Wangji likes giving it to him blah blah- They're horny kinksters and it's well within the realms of normal and they're obviously both fine and happy with it.
But Lan Wangji lifted a monolith WITH ONE ARM. Thousands of pounds of stone, lifted like a Chili's fajita platter. Wei Wuxian as Mo Xuanyu has a very weak golden core. He is infinitely weaker than his husband on a physical level.
Which means it stands to reason that Lan Wangji has to constantly be mindful of his safety and what his body can handle and be mindful of that even when engaging in rough CNC sex.
It's one of those things that for me highlights the care and reverence Lan Wangji has for Wei Wuxian as a person and as his spouse and lover. He spent years trying and failing to coax Wei Wuxian into a place where he already was, and in this second chance he instead meets Wei Wuxian right where he is.
I find it very sweet, actually.