So, when one of your engineers asks the respectable question: "Do we push any apps at computers in OU
Thankfully, Microsoft spent just enough time on their SQL back-end for Config Manager to make a lot of chores surprisingly simple with just a few minutes poking around in SQL Management Studio.
Here's one example to demonstrate how to identify which Collections are built on query-rules that point at AD OUs, and (AND) which have Advertisements pointed at them...
SELECT v_Collection.Name, v_Advertisement.AdvertisementID, v_Advertisement.AdvertisementName, v_CollectionRuleQuery.QueryExpression FROM v_CollectionRuleQuery INNER JOIN v_Collection ON v_CollectionRuleQuery.CollectionID = v_Collection.CollectionID INNER JOIN dbo.v_Advertisement ON v_Collection.CollectionID = v_Advertisement.CollectionID WHERE (v_CollectionRuleQuery.QueryExpression LIKE '%SYSTEM_OU_NAME%') ORDER BY AdvertisementName
Once you start scratching the SQL surface, it's hard to stop.