You don't get a lot of rich information via SNMP for Meraki - host of that comes via the API. Which monitoring platform are you using? Many like PRTG have native Meraki API monitoring support.
You can run SNMP against the cloud, or directly againt the device itself. From memory, you get more info when running directly against the device itself.
Your snmpwalk command you use is using V3, or so I not sure what you mean by enabling it - you are already using it.