I think you may have missed my point about latency and not being able to control it through your PC: USB cables aren’t the fastest in the world, and the time it takes for your phone to send the display data to the pc then monitor, then the time it takes for your joystick to send it’s signals back to your phone increase latency (basically you would see a time difference between doing something and it actually happening on screen)
To further that, as I said above, you wouldn’t be able to control the device with your PC. Especially more so on iOS, you are limited on which external devices can control your phone/ tablet. Mirroring a screen simply allows you to see your display in a larger format, but typically does not allow control (you wouldn’t be able to use a keyboard and joystick)
Liveflight is an excellent alternative, but would still require you to use the screen on your phone as the primary display, but would allow you to use a keyboard and joystick.
Hope that helps explain a bit