Korr and Amelia would be a 9.5 or a 10. They are very good with the litter box, but there might be the odd poop or pee out of the box. They have a 3 level cage and only pee and poop on the bottom where the litter box is.
Lillian is a 9 or 9.5. She is usually really good, but has some times where there is pee or poops out of the cage. This is usually when she gets veggies (she is sensitive to them) or has a fuller coat. She does have a big pen attached to her cage and hardly ever pees in it, but there are some poop (some might be from when I clean and don't clean up the pen really well).
Kraken get a 9 in the cage. He never really has any poops out of the litter box, but might pee once in a while. His cage when I clean is mostly hay. In the pen, it is another story and he doesn't use the litter box at all. He does use the same areas to pee, but poops end up all over.
Tesla would get an 8 in his cage. He mostly uses the litter box for pee (there are sometimes that he does not and that is usually when it is getting dirty). For poops, he is pretty good but there do tend to be some out of the box. He does have a small box (won't use anything else), so that could be part of it. Again, in the pen all bets are off.
Gizmo and Nala get around a 5. They will use the litter box, but it's maybe 50% of the time. There are lots of poop around the cage and pee on the blanket.