single.php

<?php

/**
 * Post Title Width
 * @see https://www.billerickson.net/change-width-of-post-title-in-gutenberg/
 */
function be_single_post_title_width( $attr ) {
	$custom_width = intval( get_post_meta( get_the_ID(), 'ea_post_header_width', true ) );
	if( empty( $custom_width ) || 1168 == $custom_width )
		return $attr;

	$attr['style'] = 'max-width: ' . $custom_width . 'px';
	return $attr;
}
add_filter( 'genesis_attr_entry-title', 'be_single_post_title_width' );