You're on the right track, cfarmand.
You may notice some information is missing or different when you convert your data from QuickBooks Desktop (QBDT) to QuickBooks Online Accountant (QBOA). This is due to QBDT having more features than QBOA.
If you think those are the same customers or suppliers you can merge them. This moves the data to the customer profile you want to keep.
To answer your question about QBO Bookkeeping company name have top priority is yes. Since this can affect other users if you set up limited access to your team.
For future reference, I've added this article to help you manage your team to help you with your firm: Add and manage your accounting team in QuickBooks Online Accountant.
Please let me know if you have further questions or concerns. I'll be here to help you.