Hi there,
the only way of excluding a taxonomy is by deselecting it from the list of terms. There is no display all but exclude ‘this term’. You can set the Offset in the Settings tab. So for example if the first (grid) list and second list were set to just display all recent posts. In the second list you can set the Offset to 5, this will then exclude those shown in the top list.
Its one downfall of using flex to create the rows/columns as they will size themselves to the largest element in the row. We can target that specific list by its ID and scale up the Image container to get around that, it does mean less of the image will be show. Here is the CSS for that:
#wpsp-1471 .wp-show-posts-image.wpsp-image-center {
transform: scale(1.3);
}