First of all v sync enabled in the game if it has the option, will limit the frame rate to match the refresh rate of your monitor.
But I take it you already know this.
Disabling it though can lead to screen tearing while playing the game.
Some games just have a set highest FPS target.
And why you often see no improvement in a game even if you lower the screen resolution or the graphics detail settings, and fx of the game.
The draw distance value set in a game can also sometimes impact on frame rates because there is more graphical load the Gpu needs to draw in the rendered display output to the screen.
So if there is an option of draw distance sometimes by lowering it you can gain a few extra frames per second in a game title.