You can see some graphs in Security & SD-WAN > Device Status in the Meraki dashboard.
You can also see some in Network > Monitor > Clients. This page shows detailed usage data by client, including application breakdowns.
Organization > Summary Report provides an overview of device usage, including the MX device.
And you can do more detailed traffic analysis by going to Network > Traffic Analysis.
Clients Usage Page Overview - Cisco Meraki Documentation
Device Utilization - Cisco Meraki Documentation
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
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