Perhaps worth noting that, I’m not sure if it’s a conflict with WP Show Posts, but the added feature on GeneratePress, namely Blogs (Customizer > Layout > Blog) has zero effect on any of the blog types (Archive, Posts, Pages).
I created a post and using WP Show Posts, inserted the shortcode to my homepage, and all is well with the posts displaying, including images (defined in WP Show Posts). However, when clicking through to the actual full post, it does not display the featured image. As there is no option for this in WP Show Posts, I figured this aspect of the posts were controlled by the Blog add-on in GP Pro. I disabled every check-box, and it had zero effect on the post.
So I’m not sure how well these two play together – I’d like to have the featured image display on the main blog post, but nothing’s working.