Notes storage: part iCloud part iMac

at the moment all my notes are stored on iCloud. But it is telling me I’m running out of space even though my total usage is only 3.5gb. There are some notes that I want available on all my devices but I don’t need them all. Is it just an on/off thing or can you have some notes in iCloud and some not? And if so, how do you move individual notes out of iCloud.