Backdrop CMS is based on the works of Drupal 7. It can be viewed as an extended version of Drupal 7 and branched off from Drupal 8 during the development cycle at a time when Drupal was getting completely refactored to include some Symfony2 framework and moving towards OOP while maintaining the Drupal UI and concepts.
I'm not entirely sure why CSF on CentOS 7 sends out excessive resource usage email alerts. But it gets annoying when you have several dozen websites hosted on the server.
cPanel v58 with EasyApache 4 allows users to override default PHP config values by placing a custom php.ini in domain's webroot.
There are certain tasks in Drupal modules that requires a Cron job to be setup.