After a little bit of research:

So for those who want to do this at 1080p, you can, but the graphics settings will have to be turned down to achieve the constant 30FPS mark. So we will be doing this at 900p. Don't worry though, you will BARELY notice the change AND you will still be playing the game on HIGH settings.

The Guide Starts here. (You can tweak some settings if you don't like them)

So the first thing you want to do of course is to hop over into your Graphics settings and go to

POSTPROCESSING.

MotionBlur: ON
Blur: ON
Anti-Aliasing: ON
Bloom: ON
Sharpening: Doens't matter (I keep mine on LOW because that looks best to me)
Ambient Occlusion: SSAO or OFF, SSAO looks better compared to OFF and HBAO+ takes away about 5FPS
Depth of Field: OFF (Hate it in my opinion but leaving it off saves valuable FPS)
Chromatic Abberation: ON (Notice no impact or visual difference)
Vignetting: ON (Doesn't hurt anything and is kind of pleasant)
Light Shafts: ON

GRAPHICS.
VSync: ON
Maximum Frames Per Second: 30
Resolution: 1600x900
Display Mode: Full Screen
NVIDIA HairWorks: OFF (Just DESTROYS FPS)
Number of Background Characters: LOW (You will never see an insane amount so keeping this on LOW saves FPS)
Shadow Quality: HIGH
Terrain Quality: HIGH
Water Quality: HIGH OR ULTRA
Grass Density: HIGH
Texture Quality: HIGH
Foliage Visibility Range: MEDIUM
Detail Level: HIGH
Hardware Cursor (Mouse Acceleration): OFF

Now you should have no problem running the Witcher 3 and can enjoy the Story without any hiccups. Let me know if this helped you guys out.

Source: http://steamcommunity.com/app/292030/discussions/0/594820656477851290/