This is High Sierra release is a mess.
I am one of the «lucky ones» that have an Nvidia dGPU, and installing the Nvidia Web driver fixed it. And I can confirm that reverting back to the native driver brought the sluggishness back.
The Nvidia Web driver always checks the OS Build number and reverts back to Mac OS X's native driver if the OS Build is not listed as supported.
This is exactly what happened this morning after installing the latest security update.
I had to reboot my MBP for another reason, and after that I was stuck working an entire day with the native driver until Nvidia released an updated driver. After more than a week of my MBP running flawlessly and not even having to reboot it for 7days, it was laggy again.
Safari was slow and choppy while browsing and scrolling.
Scrolling in MS word on my 4k external monitor was painful. I did not experience the usual freeze after lunch break sleep, since I did not take a break today. No doubt it would have.
Seeing how many of us are having the issue, with or without Nvidia graphics cards, this indeed cannot be an Nvidia hardware issue, but there must be something that Nvidia are doing with their web driver that fixes the issue.
If Apple support staff/devs were were to acknowledge all our feedback on this thread and the one below, they might actually be able to find a fix for everyone.
Re: High Sierra macOS freezing and stops
It is very frustrating that this issue doesn't seem to be acknowledged by Apple support and that our pricey Apple laptop/desktop does not receive better tested OS upgrades.
I did not choose Apple and paid such a high price to deal with this kind of crap.