What changes?
When enabled, WM Guard disables XML-RPC through WordPress filters, empties available XML-RPC methods, and removes the pingback header.
Why can this help?
Many sites do not need XML-RPC, and the interface can be attractive for brute-force or pingback abuse.
Compatibility: Leave this protection disabled if you use features that require XML-RPC—for example certain WordPress mobile app or Jetpack workflows. Test the site after enabling it.