Hardware gamepads and keyboard emulators are expensive, with buttons in fixed positions, and not much customization possible. With software control panels, new layouts can be applied instantly. Change buttons and keyboard bindings on the fly right from the android app.

Launch this on any android device and the Ctrl_PC app on a PC you want to control, then select your PC's ip/port, hit connect from android, then allow the client from the PC app, and that's it. Start pushing buttons! Keyboard output will go to whatever window has focus, so you can test it with any app (notepad for example).

If you don't like the layout, change it. The button images, text, sizes, key bindings, even enable/disable any button at will to create your own custom control panel.