Is your Mac running slower than it should after the update to High Sierra?
We figured out that installing NVIDIA driver solves the issue for us. Once installed you get a new NVIDIA preference pane, where you can choose to use the NVIDIA driver or the OS X Default Graphics Driver.
For macOS 10.13.0:
http://www.nvidia.com/download/driverResults.aspx/126157/en-us
For macOS 10.13.1:
http://www.nvidia.com/download/driverResults.aspx/126538/en-us