apply_filters( 'relevanssi_related_wide_limit', int $limit )
This filter hook adjusts the character count that controls when Relevanssi makes a Related Posts post element wide.
Parameters
$limit
(int) The number of (multibyte) characters, default 100.
More information
Relevanssi prints out Related Posts with the default template, with each post in a div element. The div elements have a class relevanssi_related_post, and if the element has enough text, class wide is also added. With the default styles, the class makes the element span two columns in the grid.
The limit for the wide class is 100 characters. If you want to modify that limit, add this to your site:
add_filter( 'relevanssi_related_wide_limit', function() { return 200; } );