Hi @Anonymous ,
Based on my search, two similar answers to your questions have been adopted, which proves that this is a credible process. Please refer to:
Moving GoDaddy Office365 to Microsoft Office365 Step by Step - Microsoft Community
Migrate Office365 from Godaddy to Microsoft - Microsoft Community
As for the impact of migration on users, how long will it, it can depend on how much data is going to be migrated, the network conditions: Migration performance factors. I suggest you send a notification for users for upcoming migration and service changes.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.