I have a 144 hz monitor and I have adjusted the resolution setting in the game to be at 144 hz. When I start playing the game, the in-game fps overlay shows 144 hz, but the game looks like it is running a 60 hz. I just upgraded windows and I did not have this issue previously. Also I have made sure that the refresh rate is set to 144 hz in the windows display settings as well.
Uncheck the full screen optimization option in the properties for Overwatch.exe and Overwatch Launcher.exe. And then set your fps to something slightly higher than 144.