Hi,
I did a bit of testing by changing both the resolution and refresh rate on my two monitors. I confirm that for me the multiscreen works well in Windowed mode, but in FullScreen mode, in any case FS freezes when I release the instruments window on the second monitor. The graphics card is an NVIDIA GeForce GTX 1650 and the monitors are a 27-inch 165hz and a 21-inch 60hz, but even if I set them both to 60hz the result is always the same: it freeze.