I'm returning the Lenovo Carbon X1, so that is not a problem anymore. But I still have doubts that windows version could be causing anything - My HP display at home has since 5 years been completely problem free with all the latest Windows updates. Even now with the Creators Update.
I have just tested a HP laptop with Windows 7, which caused this round of laptop switching. That HP had the same flicker as the Lenovo has, though that neither had any PWM at 100%.
Though another HP with no PWM at 100% was not causing eye strain with Win 8, but then with Win10 it does. But that also has the same flicker that the Lenovo has. There is though a chance that 3 years ago when I was using the HP, my eyes were not so irritated and I didn't notice the irritation. I simply don't know - there might be a small chance that with certain displays, a driver or windows version is in fact doing something that is irritating.
But sill, this HP 27 inch display does not irritate even with the latest Windows versions. I have an Nvidia GTX display adapter though, so no intel drivers as with all the laptops. The intel drivers could be the culprit.
But PWM without any doubt a problem for me, as I have confirmed dozens of devices to cause no eye strain, when there is no PWM. E.g. Surface PRO 2 at 100%, Surface Pro 3 at over 60% brightness, several phones, several samsung displays and televisions.
But now it seems that some other type of flicker that is not really PWM is causing additional eye strain in some displays.