Backup

Hi. Sorry, I am not sure about whether you can check each of it to know which documents are in it. I am only sure that you can select which apps that you wish to backup. But you can check the size of the backup of the apps to know which apps take up the most space. If your apps that you selected for backup exceeds your iCloud storage size that you have, you will not be able to backup. I tried before.

You can go to Apple ID, then go to iCloud, then go to Manage Account Storage. You can select those apps that you wish to delete from your iCloud.