Not sure if this is relevant or will help, but,
One thing I have noticed, (On Linux, but probably true on Windows)
I could not place a Monitor of another GPU in between two other monitors of another GPU.
Example of Invalid Scenario for my triple monitor system, Nvidia, Intel, Nvidia
(Also Linux monitor placement is soo much easier, thier must be a config for windows somewhere?)
The NVIDIA Panel in Linux supports both Nvidia Monitors and Intel Monitors, I was able to fine tune via that. Is that not an option in the Windows Version?