I am working on this now. One piece of information that is missing from the documentation:
https://knowledgebase.ajaxsearchpro.com/hooks/filters/query-and-output/asp_query_args#primary-and-secondary-ordering
You can set the primary search order to
Primary ordering: Custom Field descending
custom field name: views
type: numeric
how would you use that in
$args[‘post_primary_order’] = “relevance DESC”;
?