Splunk is for visibility, dashboards, and alerts.
The XDR Platform is for incident response, threat intelligence, and correlation. Optionally, the Merak Dashboard/API is for direct device visibility or configuration.
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
Please, if this post was useful, leave your kudos and mark it as solved.