Where is the supporting documentation

There is no supporting documentation.

To add forms, tables, or any other elements, just add HTML. You can add HTML using the Text editor (not the Visual editor).
HTML Forms
HTML tables

The Preview is just to show you what the styling looks like for a particular theme. The Preview may not (and most often is not) an accurate portrayal of what the theme layout actually will be once you install and activate it.

Many thanks for pointing this out.
Yeah, I’ve done some HTML stuff for clients, but more recently, clients want something that gets them going and then they want to look after it themselves with some guidance. Thus, a Theme with built in Tables is cool, and of course, there are plugins as well.
Cheers.

hello

here you have some demos …

https://www.designbombs.com/master-twenty-sixteen-wordpress-theme/
How To Master Twenty Sixteen (Or Any WordPress Theme)

In this post we look at how to bend the twenty sixteen theme to your will, both inside and outside the admin area and customizer.
If you’re new to WordPress, working with a well documented theme like Twenty Sixteen or any of the other official WordPress themes, can really help your learning curve.
In this tutorial, we will cover three different areas to learn to master, and we’ll separate them into three different difficulty categories.

hope that helps

say

Many thanks for the website reference, it looks like a great read and study.