For me the NVWebDriverLibValFix.kext does not work at all. Once nvidia web driver is installed, my PC just keep restarting after booting, nothing I do get pass that point, nor I can enter the OS (-x doesn´t work, nor disabling Nvidia web flag in Clover, nor nv_disable=1, etc).
My card is a GTX 1080, not sure if anyone here has had success with this card and the Nvidia web drivers released today for High Sierra, my SMBIOS is 18,3 as well (with a i7-7700K CPU). So far, any of the methods described here in this threads have worked for me.