The Office 365 guided setup helps you create a server plan to use for Exchange Online and an Exchange Online app that will contain the mailboxes that you want to back up.
In the guided setup, you can use either the express configuration option or the custom configuration option:
Express: The express configuration automates some configuration steps, but it requires you to use the Office 365 global administrator account and to temporarily disable multi-factor authentication for the Office 365 global administrator account. Use this option if the same person performs the roles of backup administrator, Office 365 administrator, and Azure administrator.
Custom: If you don't want to use the Office 365 global administrator account, or if you can't disable multi-factor authentication for the global administrator account for security reasons, use the custom configuration option. The custom configuration is a manual process. Use this option if different people perform the roles of backup administrator, Office 365 administrator, and Azure administrator.