The dropdown of post types will only show what is available – so in my video I had WooCommerce activated which is what made “product” available.
I believe attachment was removed for now as there was some issues with it.
With a fresh install, the only two post types available should be “post” and “page”.
I wouldn’t typically use the plugin to display pages unless it was a unique use-case. It’s mainly geared towards displaying posts and other custom post types.
You can create a list to display only posts in a category by choosing the “Taxonomy” option – in your case it would be “category”.
Then another field will display below it, where you can choose the “Term” – the name of your category you want to pull posts from.
Let me know if that helps or not 🙂