Montrer mes photos dans MacBook mais pas dans mon tél cell et ma tablette Apple

The simplest way to avoid Lightroom Desktop photos showing up on your devices is to not install the Lightroom Mobile apps on your tablet/phone. 

If you need these apps on your devices but do not want your pictures to sync from the desktop/cloud to your devices, then having those devices log in via a different Adobe ID than your desktop is one way to go. If you rely on getting the device photos to your desktop, then you would Add them via a cable connect and import operation.