Many SMB customers have been purchasing Office 365 E3, but we recommend evaluating if the customer is using any of the capabilities that aren’t provided by Microsoft 365 Business. Microsoft 365 Business provides additional device management and protection capabilities that would need to be added to an Office 365 E3.
If Microsoft 365 Business doesn’t include all of the Microsoft 365 capabilities that a you need, you can add many of these services as additional SKUs.