The way I understand it tripple buffering adds latency in exchange for higher sub display hz framerates.
Double buffering renders the next frame while displaying the current. That results in latency of 1 frame since input. Triple buffering adds another frame to the queue, resulting in a 2 frame lag.
With double buffering the framerate gets cut in half if it cannot meet vsync, with triple buffering it can also get cut in thirds. So double buffering is 60 -> 30, where the frame lasts 2 refreshes. Triple is 60 -> 40, where one frame is displayed for 1 refresh and another is displayed for 2.
Nowadays it's probably better to use adaptive vsync, which simply disables vsync when the framerate drops. This will reintroduce tearing, which might be preferable in fast action games.