What kind of pen or stylus should I use?

You can use any capacitive stylus compatible with your device.

A capacitive stylus has a firmer and smaller tip like a ballpoint pen. This type of stylus has a battery that must be charged from time to time, depending on the usage.  This type of stylus is typically used for note-taking, document annotating, on-screen drawing and/or painting as well as accurate object selection and scrolling.

This type of stylus is preferred for the above-mentioned as it is more sensitive to pressure and tilt which allows for more precision and accuracy.

For iOS users, the best option is the Apple Pencil. There are two versions of the Apple Pencil, one released in 2015 and the second version released in 2018. The two do the same thing, but have different designs and charging mechanisms.

The biggest difference probably is the device compatibility – Apple Pencil 2 works with the 2018 ‌iPad Pro‌ models and Apple Pencil 1 works with everything else.