Trouble getting 60 fps constant in rise of the tomb raider

I have a gtx 1060 and just launched the game today, with some settings on medium and dx12 off i expected a smooth 60fps like shown here : https://www.youtube.com/watch?v=frNyt96l28c But i drop between 40-50 fps, what's wrong ?

Also, since the game automatically limits fps at 60, should i assume vsync is enabled and is giving me 30 FPS when i drop under 60 ?