okay with a 100hz panel you may expect FPS to be a little less. So it doesn't sound as if it's completely out of whack.
You can set game settings in two ways. Through the in-game settings or via the Nvidia control panel. Right click on your desktop and you should see the option on the menu, click it and open it up. Then go to 3d settings. You can change some variable here, including optimizations. You can enhance the application (game) settings either Gobally (which means anything you change will be applied to all 3d apps) or per game (which will only apply the changes to the specific game profile)
Sometimes to get best FPS you need to play around. Peronally, even though my own system runs everything I want at Ultra @ 1080p, I will often turn of MXAA or AF or some postprocessing effects, as they can impact FPS massively. But everything else will be on Ultra.