Decided to do a big comparison of a lot of the graphics settings to see what the effect of some of them are, and how big of an impact they have on framerate. This was done at 2560x1440 with this rig: i7-4790k, GTX 980, 16gb ram.
Optimization mode (144fps) - Kinda looks like an early 2000's game (capped at 144fps because of my monitor's refresh rate).
Very low (136fps) - Actually looks like a modern game.
Low (132fps) - Better shadows and foilage in the distance.
Medium (100fps) - Thicker foilage at close distance, better shadows at a distance, and more objects rendered further away.
Slightly high (82fps) - Tesselated terrain and better foilage shadows?
High (69fps) - Better LOD and SSAO gets toggled on.
Very high (68fps) - Even better LOD.
High end mode (43fps) - Much better LOD.
No anti-aliasing (43fps)
Anti-aliasing (43fps) - FXAA post processing.
No SSAO (50fps)
SSAO (43fps)
No improve distance (43fps)
Improve distance (39fps) - Improves mountains in the distance (tesselation?), but currently has a bug which sometimes causes gaps.
No filter (43fps)
Vibrance filter (43fps) - This filter is on by default.
No upscale (43fps)
Upscale (63fps) - Not sure which resolution it upscales from, but it has a surprisingly low performance gain.
No crop (43fps)
Crop (110fps)
No screen filter (39fps)
Screen filter (39fps) - Blurs everything at a certain distance.
2560x1440 (43fps)
1920x1080 (67fps)
1280x720 (110fps)
Some thoughts: I personally think the game looks more natural without the filter, so I suggest people try that and see what they prefer. I also personally prefer both "depth of field" and "screen filter" off to remove blur. High end mode is only really realistic if you have an extremely beefy rig or you're taking screenshots. You get more LOD pop-in if you use a lower setting, but the performance hit is huge with high-end mode.
Some areas have awful framerate no matter what. For instance, Calpheon will drastically reduce the framerate, and there's this weird spot southeast of Hidel which destroys the framerate if you look towards Hidel (getting closer to Hidel from that spot improves the framerate, oddly enough).
Unfortunately, the game applies a sharpening filter which is always on. It looks passable if you have AA on, but I really wish you could turn it off.