You can make some useful changes to your fallout ini file and the enblocal.ini file included. Find your Fallout by navigating to documents/my games/falloutnv.
If you're on Mod Organizer, click the puzzle pieces at the top to configure the same.

[Display]
iShadowMapResolution=1024
fLightLODDefaultStartFade=10240.0000
fLightLODRange=10240.0000
fLightLODMinStartFade=10240.0000
fLightLODMaxStartFade=10240.0000
fSpecularLODDefaultStartFade=10240.0000
fSpecularLODRange=10240.0000
fSpecularLODMinStartFade=10240.0000
fSpecularLODMaxStartFade=10240.0000

iShadowMode=3 (At falloutprefs.ini)

Increase your grass density if your system can handle it!

[Grass]
iGrassDensityEvalSize=3
iMaxGrassTypesPerTexure=6
iMinGrassSize=50 (The lower the value, the higher the grass density; 70-80 is great for performance
bGrassPointLighting=1

With the enblocal.ini file, you MUST configure ReservedMemorySize and VideoMemorySize to conform to your computer's specs.

I have a GTX Titan, which has 6GB of memory. I would input VideoMemorySize=6144 <----(6GB converted to MB)
You will need to consult the internet to find you graphics card's VRAM specs.

Leave FixTransparencyBugs to false unless you want transparent ceilings!