Can I use my iPad Pro for Layout. Do I need to download an app to use Layout?
LayOut is only available on Windows and Mac OS. There is no LayOut for iPad at this point in time.
However, if you have both a mac and and ipad, you can (temporary) use your ipad as an external secondary screen.
doing so, you’ll be able to have layout on your ipad pro. there you might be able to use it with your stylus and/or fingers, but keep in mind it’s in no way optimised nor thought for this use.
It’s supposed to be mouse / keyboard.