Post FX for example disabling that gives a massive increase in fps but that's because most of the lighting effects are under that setting, so you are effectively lowering the lighting for extra fps.
That's not something I am personally willing to do on a high end overclocked GPU and CPU.
I think my next tweak will be dropping post fx to very high and maybe dropping extended distance scaling to 20% with any luck that will give me constant 60.
I would not drop PostFx as your next tweak. From my testing there seems to be a noticeable difference in lighting between PostFx Ultra dn Very High. Personally with my 970 its something I'm not willing to sacrifice, so I doubt you would want to as well.
My opinion is that everything in the "advanced" menu is gravy really. The extended distance scaling is just, that "extended". It looks incredible with it on especially at high locations where you can see far out into the distance, but even with it at 0 clicks the pop-in isn't that bad. I've settled for 50% for now. Also the extended shadow distance is a gravy setting too, its sort of difficult to notice the difference. I tested both sliders standing still in a spot where I could see far down the road and didn't notice a huge difference. I noticed a slight increase in car pop-in with extended scaling at 0, but not that bad.
IMO things to decrease in order if you are using a top-end card (980/970 or 290x):
1. Turn off MSAA
2. Reduce shadows from PCSS to Softest (good 5-7 fps hit on my system)
2. Reduce extended distance scaling and extended shadows sliders (mine are at 50%)
3. Reduce grass quality from Ultra to Very High (murder with high vegetation)
4. Turn off high res shadows and/or long shadows
Those are my top 4 so far. I am not currently using #4, but it does give a decent bunch of fps back. With my i5-2500k @ 4.0ghz, 970 and 8GB RAM I'm pulling a mostly locked 60fps with 1-3.
I do notice that my CPU cores are all at near 100% usage all the time. Occassionally I will get a slight hitch while driving or something. Possibly my CPU bottle necking? I might up my OC to 4.5 ghz and see if it smooths out.
I see a lot of people are really hung up on using MSAA and struggling with getting performance they want. MSAA is absolute murder in this game, I wouldn't use it unless you are running with a large performance overhead. The FXAA in this game is pretty subtle, which is good because it doesn't blur as much, but not great because there is a fair bit of aliasing while driving and such.
Good news is, GeForce Experience recommended settings were very close to what I came up with.