Apparently you can overclock the GTX 1660 Ti VRAM an extra 1000MHz and it's perfectly stable. I've played FarCry 5, COD BO3, and Minecraft with SEUS PTGI all for a few ours
MSI Gaming X Geforce GTX 1660 TI Review - Page 9 Of 10 - Modders Inc
MSI GTX 1660 Ti Gaming X 6G Review | KitGuru- Part 15
GeForce GTX 1660 Ti VENTUS XS 6G OC
Overclocking EVGA GeForce GTX 1660 Ti XC Ultra GAMING