Gintoki:
He's over all the worst sleeper to share a bed with, he's constantly shifting positions, often finding himself at the foot of his futon or close to the edge. Of course his legs and arms are in battle against his s/o in the middle on the night.
His body temperature is constantly fluctuating, one night he is extremely hot so he would throw the covers off of him, the next he could be really cold and super clingy to his s/o, asking them to drape their body over his. He won't admit it, but he likes the close intimacy of that position. But only on cold nights!
He easily falls asleep to the feeling of his s/o's fingers softly playing with his silver tresses and massaging his scalp.
Sougo:
The calmest sleeper, he can sleep in any position and probably in any location, given if he feels like taking a nap.
If he's sleeping with his s/o he would like to have their head resting on his chest with one of his arms wrapped around their body. They would generally stay in that position through out the entire night.
He actually does sleep with his eye mask at night .
Yamazaki:
Can not shut up at night before bed, is constantly telling his s/o stories of his day.
Even though he's extremely awkward about it, he likes to have someone there with him. It's sort of a reassurance thing more than anything. But he can sleep alone just fine.
His s/o shouldn't expect any late night snuggling. He sweats just thinking about physical contact with his s/o.
He keeps anpan under his pillow. wtf.
Kamui:
Is always the big spoon, especially if his partner is significantly weaker than he is. He's aware of his enemies that don't stand a chance facing him head on, so having his s/o close to him like that ensures that they're in the safest place possible.
And also, I headcanon that Kamui is actually a big fan of skin-ship towards his lover (and only to his lover) So he would be really grabby with them and tickling them.
Which, depending on their mood, might annoy his s/o.
He sleeps very peacefully, in the sense that he has no guilty conscious what so ever. So expect him to have a very serene expression when he finally calls it a day.