Aa Colin says, on my system running in 4k, this has made a big difference.
Because some of the newer modules use extremely big textures, it causes the vram on your gfx card to completely fill up, particularly the phantom and the chinook (12gig in my case), and this results in a massive fps hit as it then switches to on board memory.
By switching to medium textures I went from 20 to a solid 60 fps on these modules.
I can't even notice any downgrade in visuals although one would assume there must be something.
This will be even more effective in vr, which Is more vram dependant.