vsync can limit your FPS however it could also be your screen limiting it, I find that adaptive Vsync works like a dream for me, I have a 780 though so I get 99999 FPS on everything
So yeah I would recommend adaptive if that works for you as it does tend to limit your fps less than normal vsync. As for multi-player games I don't believe it does really alter your performance at all as imput lag isn't really a thing, its more like output lag really as with the delay for your screen to display is the thing that delays your reaction time, when you click for example that is sent out to the server at the speed of your connection and then your screen displays that you have done it which doesn't influence your reaction at all. Its a little complicated but yeah
Thanks
Mcdonh