What is the biggest Graphics Setting change I can make to free up more FPS?

Disable PostFX? What other settings can I change to get another 10-15 FPS, especially on the larger terrain maps?

 

Lighting is another big one.

 

Shadows, mesh, Dynamic Reflections and SSAO. Everything else is minimal performance hit

 

The way I run, since I have integrated graphics and a good processor, is this:

Medium on Detail + Mesh
Lowest on Lighting + Shaders
Dynamic Reflections are optional, don't have much FPS hit

Lighting is a FPS killer. Turn it on lowest and it disables it and the game runs a lot smoother.