Nvidia guide Check that for references, they will show some screenshot comparisons and show a meter to say how much of a performance difference some options take.
If you want an easy list:
Demanding options: HairWorks, Anti-Aliasing, HBAO+/SSAO, Foliage Visibility Range,
Non-demanding: Bloom, Blur/Motion Blur*, Chromatic Aberration, Depth of Field*, Detail Level*, Grass Density, Light Shafts, Shadow Quality*, Sharpen, Terrain Quality**, Texture Quality*, Vignette, Water Quality
* These can be more or less demanding depending on situation but in most cases less so.
** Terrain Quality according to the Nvidia Guide is supposed to utilize tessellation on geometrical textures but apparently it either doesn't work or it's not implemented because they didn't notice any drops (or heavily optimized given their test system runs 2 Titans in SLI).