This is a pro feature. You can show only posts and pages from the free version of the plugin.
The Post Grid plugins supported all Custom Post Types (CPT). That means if you would like to show posts from your own CPT then you can do it by the plugin. But there is a little difference between the shortcode version and the Gutenberg/Elementor version.
If you use the shortcode then you can build your query by filtering all Custom Taxonomy but you will not be able to show the Custom Taxonomy as meta on the post.
But If you use the Elementor or Gutenberg version then you can build your query by filtering all Custom Taxonomy and also will be able to show all categories on the post as meta. Please watch the below video to know how will you do it. It has been shown this step by step from Shortcode to Gutenberg.