Refer TagManager API https://developer.adobe.com/experience-manager/reference-materials/6-5/javadoc/index.html?com/day/cq/tagging/TagManager.html 

If you have any specific storage sizing requirement , better to connect with Adobe support team .Meanwhile you can referhttps://experienceleague.adobe.com/docs/experience-manager-65/assets/administer/assets-sizing-guide.html?lang=en  

Refer : https://experienceleague.adobe.com/docs/experience-manager-cloud-service/content/sites/authoring/projects/managing.html?lang=en#deleting-a-project-or-resource-linkIt may help .

Refer https://experienceleague.adobe.com/docs/experience-manager-xml-documentation-learn/videos/getting-started/understanding-the-aem-user-interface.html?lang=en  

New Relic One application performance monitoring (APM) service for AEM as a Cloud Service is added in cloud manager for all the customers .For more details refer https://experienceleague.adobe.com/docs/experience-manager-cloud-service/content/implementing/using-cloud-manager/user-access-new-relic.ht...

Check the report tab in cloud manager .As of now i  can only see SLA report due to user role .But as per documentation you can view Storage tab as well https://experienceleague.adobe.com/docs/experience-manager-cloud-manager/using/how-to-use/monitor-your-environments.html?lang=en#system-monitoring-o...

Refer : https://experienceleaguecommunities.adobe.com/t5/adobe-experience-manager/error-failed-to-execute-goal-com-github-eirslett-frontend-maven/td-p/439761 

From Admin console https://adminconsole.adobe.com/ you can check  . Refer : https://helpx.adobe.com/enterprise/using/admin-console.html Thanks 

Refer https://experienceleaguecommunities.adobe.com/t5/adobe-experience-manager/dispatcher-clear-cache-curl-no-longer-works/td-p/383165 

Configure ACLs according to user accounts to allow (or disable) starting, and participating in, workflows.Refer : https://experienceleague.adobe.com/docs/experience-manager-65/administering/operations/workflows-managing.html?lang=en