Unfortunately, there are no scripts in our repository that can be used to achieve the desired. However, it can be done without scripts. To cancel all meetings organized by a user, the corresponding action can be executed in a custom command, scheduled task, or business rule. To enable the Automatically decline new invitations option, you can use the Modify Exchange properties action. The option is available on the Automatic Replies (OOF) tab.
If you still need to manage the options via a PowerShell script, here are the links to the corresponding methods in our SDK: