Understanding G-sync

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I'm getting a bit confused.

Am I right in saying that to make use of G-sync you need to do the following:

1) Enable G-SYNC in NVIDIA Control Panel
2) Manage 3D settings -> Monitor Technology > G-SYNC
3) Vertical sync -> On

Is this correct? I *need* to have V-sync enabled to use G-sync? If I have V-sync off and G-sync on, it won't work at all?

 

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Also another question. Using the 3 steps above, that will introduce input lag, so in games like CS:GO you don't want to do this, however, if you set fps_max 140 in CS:GO, you won't get input lag, but have the benefit of G-sync, right?