iCloud Drive

Read the articles https://support.apple.com/en-in/guide/icloud/mmd0b4a7f5e8/icloud

For back ups https://support.apple.com/en-in/HT203977

https://support.apple.com/en-in/HT207428

The purpose of iCloud Drive is mentioned in the first article and not used for iCloud back ups .

iCloud Drive will accept most any file type.

What type of backups are you planning?