Really no software needed, unless you want to use a touch enabled screen and/or you want the instruments to automatically pop out each time you start up a flight…if either of those are true for your situation, check out MSFS Pop Out Panel Manager. It’s free at flightsim.to and is a great little mod.
But if you’re just wanting to pop out panels to other screens, all you need to do is hover above the panel you want to pop out (and assuming it CAN be popped out) you can just use right alt + left mouse click and it should pop out. Then you just drag to whatever screen you want.
As far as additional monitors for additional cockpit views, someone else already covered that above with the built in multimonitor/render window function in the game itself. I saw almost no noticeable performance hit popping out my instruments, maybe 2-3fps total in the end. That being said, my 3090 only has 4 ports on it, and 3 of them are taken by my main view monitors. I also have a motherboard that allows for 2 display inputs, which I used, and then added one more using a usb 3 to hdmi adapter (adapter has a built in graphics card that is good enough to just display an instrument panel).
Hope that helps.