Some more tests...
Here are the specs for my work laptop:
ASUS running Windows 10 (64 bit)
Intel I7 2.6 GHz (8 CPUs)
DirectX 12
GeForce GTX 970M
I have two external monitors, a Dell and a Lenovo. I ran some tests using my laptop monitor as my "main" screen, and more tests after making my Dell monitor my "main".
LAPTOP MONITOR IS "MAIN"
LAPTOP MONITOR
The demo runs like butter. The vehicle and the background are perfectly smooth. No microlags or jerkiness at all.
SECONDARY AND TERTIARY MONITORS
The vehicle and the background show pronounced jerking and lag.
SECONDARY MONITOR IS "MAIN"
LAPTOP MONITOR
The vehicle and shadow look perfect but the background has some slight jerkiness. It is MUCH better than the jerkiness mentioned above.
SECONDARY AND TERTIARY MONITORS
The vehicle looks perfect, but the background looks a little blurry? (As if it was being rendered in a location and then a millisecond later rendered one pixel to the left or right.) Despite any possible blurriness it still looks great.
It will be interesting to see if the new C3 runtime makes this better!