If you decide to not to have legal hold, then you do not need E3. Since I am not sure what else you need, have a look again on where the Mac software can be found -
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, and Office 365 ProPlus A for Students
However, if you require Exchange Online Plan 2 AND Office for Mac then E3 is the right choice.