If a Mac is within the included range of supported models for an OS, then it should run without problem.
One of the reasons for Apple excluding a Mac from a new OS is that the 'experience' is not good enough, in terms of speed.
I've run all three OSes on a 2014 MBP, and performance was fine. I didn't notice any discernible difference.
It has just happened to me as well.
For me, it turned out that a specific app (VPN) has blocked the input from my keyboard. When I closed the app, the keyboard immediately returned to work properly (no reset was required).
Try to close apps that start-up with your Mac, prehaps one of them is taking control over your input.
I had a similar bug happen to me. A fix I found was to make the window fullscreen and then not fullscreen. Being that you likely can't see the fullscreen button, another option if you already know the window is maximized (not fullscreen), it to put open another window of the same size, layer the invisible window on top of it, and then move the mouse over to ...
Unfortunately, it does not necessarily not transfer what you tell it not to transfer, nor does it for what you do tell it to transfer for that matter. I told it to exclude one of the users, and that was honored. However, I told it not to transfer certain folders, but it did that anyway. I told it not to import printer settings, but it did that anyway. I told ...