Suppose I'm using the Salesforce Composite Connector in Mule to query 3 different objects in Salesforce, What are the limits to the number of records returned by each query?
The connector doesn't impose limits. The limits are the ones defined by Salesforce for queries: https://developer.salesforce.com/docs/atlas.en-us.salesforce_app_limits_cheatsheet.meta/salesforce_app_limits_cheatsheet/salesforce_app_limits_platform_soslsoql.htm