This mod only affects the hairstyles showcased in the screenshots. The optional files are standalone and affect only what the descriptions say.

FPS Comparison:

I've been playing with the HW settings for some time now, trying to find the best configuration that would suit my tastes and make this setting less demanding and this is what I've come up thus far. The results may slightly vary from the screenshots as I'm constantly tweaking the settings trying to get even better appearance without performance loss. The old files are available if you don't find my newer tweaks appropriate for you.

The Reduced Collision version is always the most up-to-date because that's the one I play with. The others will be updated less frequently. 

Depending on your specs you can probably expect up to about 10 fps boost in normal gameplay.

List of changes:

• The amount of hair strands reduced to the absolute minimum that doesn't make Geralt look balding (the crown hair are now significantly thicker than the rest, because they only go along the head and don't utilize the benefits of HW technology besides the ability to get wet)
• More "puffy" hair by reduced clumping (no more pasta-hair)
• Increased curliness so the hair look more disorderly to simulate Geralt's lifestyle (no more magical shampoo)
• Wind noise reduced by half to make the hair behave in a more natural manner
• Disabled glint so light doesn't shine through the strands. It may look a little bit worse in weak light right now, but the hair are no more ridiculously ugly in strong and direct sunlight.
• Shadow reduction, boosts fps by a miniscule amount but makes the thicker hair look better
• Changed beard density
• Sligtly reduced detail LOD distance so the hair assume higher tesselation when the camera is closer to the head than in default.
  
  

I also uploaded a version where the collision spheres are reduced in size so the hair are more adjacent to the armour. May not work with all kinds of armor, I only tested it with Manticora set. Mind that these were edited "blindly" and will never fit perfectly if the hair are supposed to move. 

Per request I also uploaded an optional mod that decreases the wolf fur quality for additional fps. The alternative version leaves the detail LOD fur high quality (but still with a partial reduction in the density), the LOD distances are the same.


COMPATIBILITY: It will not work with mods that change the physics of Geralt's hair. If you want to combine it with a mod that changes the hair's color, load this mod after the color changing one. Can't guarantee it will always work. 

It should work even with most other mods that change Geralt's hair properties, but I can't predict the results. You can try and experiment yourself, it won't break your game. Just remember that the load order will often affect the final appearance, for example, if RealBeard is loaded before this mod the beard will have lower density than if it was loaded after, but in both cases, the beard's hair will have the same width.  
As of 1.7 and above the mod no longer makes any changes to the beard, but the principle about using multiple mods changing the hair stays the same. 


NOTES:

The screenshots above were taken also with the RealBeard mod.

Additionally, they were taken with a little tweak in the rendering settings. To achieve the exact same effect (and about 2-3 more fps) go to The Witcher 3 Wild Hunt\bin\config\r4game\user_config_matrix\pc, open the rendering.xml with a text editor, find the line:

<Var id="Virtual_HairWorksQualityPreset" displayName="hair_works_preset" displayType="OPTIONS" tags="refreshEngine">

and below it replace one of the presets (low or high quality) with these lines:

<Entry varId="HairWorksGlobalStrandSmoothness"value="3"/>
<Entry varId="HairWorkstGlobalDensityLimit"value="1"/>
<Entry varId="HairWorksGlobalDensityQuality"value="1.0"/>
<Entry varId="HairWorksGlobalDetailLODFactor"value="1"/>
<Entry varId="HairWorksGlobalWidthLimit"value="2.25"/>

These changes are global, so they will also affect the monsters and animals with HW. The difference in appearance is hardly aparent during gameplay, but the fps boost in more demanding situations (like wolfpacks encounters) is noticeable. 

Remember to change the in-game HW quality settings after this modification.