If you want the document to be accessible on your Mac and on the iPhone/iPad then you want it stored in iCloud Drive. That way will it will sync.
Storing it in iCloud Drive doesn't mean you are collaborating. You would have to specifically turn on collaboration.
You can store it in local folders if you want, of course, but then it won't sync. On the Mac just move it using Finder from iCloud Drive to another location. On iOS/iPadOS tap the three dots with a circle around them, choose Move, and navigate to the folder you want.
Should you delete the Numbers app on iOS/iPadOS I believe you can lose locally stored documents as well.
For that reason I always keep my documents in iCloud Drive.
SG