G-sync supposed to limit my fps ?

If so then why do I notice tearing in almost every game that exceed 120fps ? Even frame limiter in games doesnt exactly limit it and also it feels laggy in full screen mode but not borderless windowed .. and im 100% sure G-Sync is enabled but I really cant see that its doing what it supposed to be doing can anyone who has G-Sync show me what is the exact settings in Nvidia panel to use I want to know everything related to G-Sync in order to make sure it does work plz.