Is there a way to access/see all files stored in iCloud to one account? I am aware that there is a online view under icloud.com, and there is a OS X and iPhone app for iCloud.

Why I am asking, is:


  I deleted all of my iCloud files (so I thought), and emptied the whole
  drive. One year later, I installed 1Password on my Mac, activated
  iCloud Drive again, and there it was: "Do you want to use your old
  iCloud file?"


So there are hidden files which stay there, no matter what.I thought I deleted everything, but somehow there were files missing or still there.


  So what is the best way to view the iCloud Drive content?
All of your iCloud Drive content will be shown here: https://www.icloud.com/#iclouddrive. 

However, 1Password does not store data in iCloud Drive: it stores your passwords (encrypted) in iCloud Documents and Data, which is a separate part of iCloud. 

To access your Documents and Data, on an iOS device: open the Settings app, go to iCloud, tap Storage, and tap Manage Storage.

You'll see a section called Documents and Data under the Backups section if you do indeed have documents and data stored in iCloud. You can edit/delete the data of each app here.