How do I move my files from the underused ICloud plan under my Apple ID, to the family sharing APPLE1 plan under my wife’s Apple ID?
How can I move my iCloud + files under my Apple ID to my wife’s Apple 1 iCloud storage?
Your wife can share her storage plan. If you currently have a paid iCloud storage plan, it will be cancelled when you switch to her plan. You continue to use your own Apple ID and access your storage in the same way as you always have. You don't move your files. Only the billing and amount of storage changes. See information in the following for more details: Share iCloud+ with your family - Apple Support