The way I see it, the title field is always there, and you have the date, excerpt, and image options as optional. So, the variation step could be omitted in favor or radio buttons that would show/hide the three optional fields. That way, it would be easier to switch layouts.

Also, having recently faced a similar issue on a website, I'd say that perhaps it would be worth considering an option to override the title, excerpt and even the image of an entry, if the user wants to. Here's what I mean: https://www.dropbox.com/s/53pkvfkqxs2zx09/gutenberg-story.gif?dl=0

On the example above, you can override the title, excerpt, and image and toggle the author. Maybe something similar would make sense to the Query Block as well. I found it to be particularly useful when it comes to image overriding, as many times, the featured image that is used in the fullstory isn't the best fit for an entry in the frontpage.