Reference:
https://www.amd.com/en/technologies/eyefinity
I am not sure about your requirements. Your reference to Eyefinity seems to indicate you wish to have your game viewable across 3 continuous screens as suggested by the 5 screen image in the link.
However, I read your post as wanting one screen/display showing a particular window and another, second window, being
duplicated on two other screens/displays. Versus extended across 3 screens.
Windows does allow multiple monitor use where a window can be PC screen only, Duplicate, Extend, or Second screen only.
Use "WIN" + "P" to see the PROJECT options.
However the Control Panel for your GPU software controls and allows other options.
May or may not be doable depending on the GPU's, the video ports and cables being used, the monitors, and the available configuration settings.
Sketch out the planned connectivity requirements show all GPU's, GPU ports, and connections to monitors.
Try to set up your required viewing environment in stages. One monitor, two monitors, and finally all three.