The Slayer :
i have a 6700K btw with 16Gb ram and i don't really need the graphics settings in advanced settings they don't really seem to make a difference in graphics but affect the performance hugely. BTW in gta 5 the Vram counter is it going to show 8Gb vram or 4Gb because i have R9 295x2 (i'm new to this whole crossfire thing.)
It will probably show 8gb but only 4gb will be usable, I would pay no attention to that VRAM counter I have found it to be absolutely useless its way off. Use msi afterburner or something if you want to measure VRAM usage. Some of those features in the advanced graphics options do quite a bit, extended distance scaling for example stand on top of mountain somewhere and play with the slider I bet you will see a difference it will render things way out in the distance that normally wouldn't even be visible without it windmills for example you have to get quite close before the windmills will pop in without that feature, ity does however affect performance I wouldn't turn it completely off but I wouldn't max it out either.