I have two mice (well a track ball and a mouse) and two monitors on my main machine - and I just plugged in a USB second keyboard to check and it works just fine. However I don’t think they work in the manner you are asking. I read it that you want two people to be able to do separate task with the mouse and keyboard. If so then I have never seen that option. Both mice operate the same pointer, just as both keyboards only work on the same active window. While it is possible to have different windows open on each monitor, it is just the one desktop and you can only have one active window.