Quick tip: if you need to grant access for your data guru who needs to see and be able to modify everything in the Insights module, you should assign them the system role: data, or any custom role that has "Manage data" permissions.
Access to Data Sources
require the Manage data permission - can be added to a custom role.
alternatively you can assign the system roles: admin or data, as they have the "Manage data" permissions included by design.
Access to Insightboards
requires Access Insightboards permission for accessing the feature.
if a user with 'Access Insightboards' and has a granular insightboard permission (for a specific Insightboard, think about this as a shared file) to edit and update a particular insightboard, they will be able to add tags, change its name, and re-arrange the insights. They won't be able to enter into edit mode of the insights and execute queries, nor will they be able to see any other insights than the one in the insightboard.
Access to Insights
require the Manage data permission - can be added to a custom role.
this permission also gives them the right to execute queries against any data source you have connected - grant this permission with caution!