I think you might be confused.
Office365 is a name to describe a suite of products by Microsoft. Exchange Online Plan 2 is part of Office365.
Exchange Online Plan 2 actually supports (meaning works with) Outlook for Mac v 15.6, unless you have read somewhere that it doesn't (please list the link here for our knowledge).
However, Exchange Online Plan 2 does not come with Outlook for Mac 15.6 as it is a server side subscription.
If you need Outlook for Mac you will need the following subscriptions, and these include the full MS-Office and not Outlook alone -
Office 365 Home
Office 365 Personal
Office 365 University
Office 365 Business
Office 365 Business Premium
Office 365 Small Business Premium
Office 365 Midsize Business
Office 365 Enterprise E3
Office 365 Enterprise E4
Office 365 ProPlus
Office 365 Government G3
Office 365 Government G4
Office 365 Education A3
Office 365 Education A4
Office 365 ProPlus for Students
Office 365 ProPlus A for Students