Autistic Gricko headcanon:
He's just as sensitive as Frost is when it comes to sensory issues. His just presents differently.
He's extremely sensitive to sound and can't handle certain noises. His hearing is very good and unfortunately that meant sometimes the others can't even hear what sound is bothering him. He fucking hates balloons popping because it always makes him jump and the shock makes him tense up in a way that hurts his neck. (I'm projecting here on this one lol, this is why I can't play games or watch stuff with jump scares it HURTS.) He can get overwhelmed by loud spaces (there's this really good fanfic on AO3 with his headcannon!) and needs to take a few minutes outside to avoid getting overstimulated. But he's also fine listening to loud rock music because it's a controlled environment and he knows he likes these sounds. Also can be self stimulatory.
He hates shoes, he hates alot of fabrics and rather stick to the small cycle of clothes he's used to. He's worn the same three outfits for years and it bothers the hell out of Kremy but Gricko to stubborn with his routine. He'll mend clothes just to keep wearing them because getting new clothes is stressful.
Not a sensory thing but I think he's very attached to his bedtime routine and likes to sleep at the same time every night as much as possible. This is why sometimes he seems stressed over everyone settling down and going to sleep while they were in the feywild.