@James12, there is capability to set rules for various traffic types, or to understand the performance of those traffic types with Meraki Insight. You'll need to be on the MX 16 firmware (beta) to get the greatest set of options for application traffic as this firmware implements the Cisco NBAR2 engine. When you're on this firmware you'll see many more traffic classes that you can shape against or define SD-WAN rules against (Microsoft Office 365 is under the 'Productivity' group).
Meraki Insight is a great tool for assisting you determine where an issue is if you have slow response times, but it really is just a monitoring and diagnostic tool.
There is also a license level above Advanced Security now, its called SD-WAN Plus. It includes the Meraki Insight capability and also adds a few extra features too. One of which is VPN Full Tunnel Exclusion based on application type. Essentially what that allows is for AutoVPN/SD-WAN to run in full tunnel mode, with pre-defined applications being chosen to not be put into the tunnel, i.e. to be excluded and have local breakout. Meraki have also hinted at additional SD-WAN specific features being added to the SD-WAN Plus license too.