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From what I have seen Three 50inch screens will work quite well with XP 10 or XP11. My final Flight sim "cockpit" will eventually have three 40inch screens. I understand you can go larger if you have the room for the installation. The 3 screens should be configured as one unit. This can be done through Windows or NVidia.
Have a look at some of the Youtube videos produced by Michael Brown at XForcePC whereby he has set up several configurations using the same screen sizes. This company is the recommended PC supplier by Laminar Research. I give you his full site as he has several other interesting bits and pieces. The link is at https://www.youtube.com/user/col2mab/videos?sort=dd&view=0&shelf_id=0 In particular in your planned situation, have a look at his last video posted 5 days ago utilising 50inch screens. Michael will also tell you in several of his videos not to waste your money on 4K screens as they will have to be "dumbed down" to 1920 x 1080 to work in XPlane.
Hope this helps
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