I have been rattling my brain over this far too long and I cannot find the solution, I have attempted plugins, to the woo commerce documentation and the storefront documenta
The following will increase products from 4 to 8 (on four columns) for "New In" section and display "Best Sellers" to a random order on Storefront Home page:
// "New In" Home products section
add_filter( 'storefront_recent_products_args', 'filter_storefront_recent_products_args', 10, 1 );
function filter_storefront_recent_products_args( $args ) {
$args['limit'] = 8;
$args['columns'] = 4;
return $args;
}
// "Best Sellers" Home products section
add_filter( 'storefront_best_selling_products_args', 'filter_storefront_best_selling_products_args', 10, 1 );
function filter_storefront_best_selling_products_args( $args ) {
$args['orderby'] = 'rand'; // Random
return $args;
}
Code goes in function.php file of your active child theme (or active theme). Tested and works.