It will depend on the need of each one, that is, the rule has no right or wrong. In some cases, some people choose to have a single template to facilitate network management. In another, people choose to have a template for each location, but this is usually when you have some particularity for each location.
And is not possible to upgrade a specific AP on the template.
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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