nyx is a pretty light sleeper, and doesn't actually tend to do it too often. she needs more of it if she spends more time as a human, but when she's being a gengar, she could conceivably go for a couple days.
she sleeps through the day, so she gets to bed in the morning after training, and wakes up some time around 4-5ish to teach her class.
she doesn't tend to use blankets because she doesn't... actually generate body heat and they would do jack shit. it's entirely possible she either doesn't own any, or gave any of the ones she does have to team
members who would actually get use out of them. she doesn't have much preference for positions, though she does tend to just flop face first and pass out like that.
may or may not float in her sleep sometimes if she goes to bed as a pogle.
also, doesn't really like excessive heat while trying to sleep, and physical contact is a little uncomfortable. very not a cuddler. exceptions might be made sometimes, but she might not actually fall asleep.
carter dislikes sleeping, and tries to do it as little as possible. sleeping itself is fine, she doesn't have any trouble falling asleep when she tries to, but she has weird dreams and she doesn't like them.
it doesn't help that she doesn't really have control when she's asleep, and especially bad/vivid dreams can have adverse affects on the people around her. "i have dreams, and my roommates get nosebleeds."
when she does sleep, it is also pretty lightly, she needs to be able to get the hell out of bed if something bad's happening. when she can, she will have all the pillows and the comfiest blanket she can find.
sleeps on her side, has a tendency to curl up. would cuddle the hell out of anyone who convinced her to let them. she could probably sleep anywhere, but she always wants to be as warm and safe as possible.
OH also clothes, nyx will either just take off outer layer of clothes and commence flop, or find a baggy t-shirt.
(she owns one of the official green fan club t-shirts for this purpose)
carter usually just sleeps in a t-shirt and shorts. for a while, she slept in her gross huge innsmouth hoodie, but now that she is in a place with actual beds for sleeping, she isn't doing that so much.