There's always been a lot of confusion with regards to where the iPad sits but its actually very simple.

The first thing to do? Forget Apple's official accessories. You can buy much cheaper versions of the Pencil from Amazon for half the price and Logitech do a great range of cases. I have a USB-C Pensil that worked with an old 8th Gen and an iPad Pro.

It then comes down to money. A customer would say "I have $400 to spend on a new computer. I only need it for $400 tasks like the web, taxes or writing a resume." in which case the 9/10th models are the $400 Apple computer aimed at people who don't want a spec-crippled Windows or Chrome device.

The Air? The $600 Apple computer.

The Pro? The $800 one.