iCloud 2TB plan vs Apple One Premier 2TB plan - impact to your iCloud data if switching?

Per - What happens to your iCloud storage plan when you sign up for Apple One - Apple Support.

"If the iCloud storage included in Apple One is equal to your current plan

During the free trial, you keep both your current iCloud storage plan and the iCloud storage in Apple One. Once the trial is finished, your current iCloud storage plan is canceled. Your total iCloud storage will be the amount included in your Apple One subscription."

TxHelp wrote:

My question: Will my iCloud data get messed up if I switch over to Apple One Premier plan 2TB from my iCloud 2TB plan?

No, your data won't "get messed up" as it will seamlessly transfer over.

What should I do if after subscribing to Apple One Premier plan and I end up with 4TB of iCloud storage (I have 2TB of iCloud storage) and I only nee 2TB of iCloud storage.

Thanks, my question is answered.

You're most welcome.