The email you got about confirming your Intuit user ID is a new authentication system required to every QuickBooks Desktop users only. Since you are subscribed to QuickBooks Online, you can disregard this email.
To give you more details and purpose about this email confirmation you can check on this link: Create and manage your Payments user ID.
If you have any other concerns don't hesitate to comment below or post again. We are always open to assist you.