Need to get 4TB of iCloud storage
I have one Apple ID with 2TB of storage that is almost full (family sharing) Let's call that Account A. I have another Apple ID with an Apple One Premier account with 2TB of storage that is empty, which we'll call Account B. My goal is to have one Apple ID with 4TB.
I believe that if I cancel Apple One Premier from Account B and buy it with Account A, Apple will cancel my iCloud storage on Account A and replace it with the 2TB from the new Apple One Premier.
Could I then purchase 2TB iCloud with Account B and then apply that storage to Account A with the result that Account A will have 4TB and Account B will have just the base plan?
Subscriptions are currently being purchased with Account B. I am not sure if I need to start using Account A for subscription purchases.
Thank you for your help.
MacBook Pro 15″, macOS 10.14