Minus scheduled jobs, everything related to the parent report (stats, drilldowns, etc.) should cascade delete when the parent report is deleted. Scheduled jobs will have to be done separately (can be done through the Reports module).
We have restricted down who can create reports simply because it got way out of hand and action needed to be taken due to the amount reaching an unmanageable size (well over a few thousand).
We will be having users go through their self-created reports to see what is still needed and will be purging whatever is left. (System-created reports not included.)
