As someone that generally just plays what they feel like rather than going for ranks I have a lot of high Bs and low As on 5*+ maps. I am not good enough to hold any kind of decent combo though. I imagine there are a lot of people around my rank in a similar position, as the game only really rewards near perfection when going for ranks.
In terms of accuracy the real difference there is HIGH OD not star rating. There are a lot of 5*~ maps with OD7 which is not very hard to acc well even if you're not good enough to hold combo. I would be more likely to get a C on a 4* OD9 then a 5* OD7.