Hi Dora,
In your case I would recommend using the custom code as described within this knowledge base article (the one you linked). It already includes the shortcode, all you need to change is the variables at the beginning, such as if you want to exclude on some pages, and the search ID.
For the plugin configuration, I would suggest this for the fixed layout: https://i.imgur.com/UZk7u7H.png
If you are using the search bar replacement feature to replace the theme search bar automatically, then I suggest making another search instance specifically for this compact box layout, to avoid any conflicst. Then use the non-compact one as the replacement.