The value stored in the database for a flex field is an array. The array contains a list, in order of the layouts that exist in the flex field. You can get this by using get_post_meta()
$layouts = get_post_mata($post->ID, 'flex_field_name', true);
if (is_array($layouts) &&
in_array('property_specs', $layouts) &&
in_array('property_overview', $layouts)) {
// both exist
}
that will tell you if both exist, but not tell you if one follows the other.