Updating WooCommerce Subscriptions Order line Items programmatically

I am trying to allow users to update line items of their subscriptions from their my account panel. I am able to get their subscription from subscription id and show them update form. Right now I show them with product items in their subscription that I got through

$subscription = wcs_get_subscription($_GET['subscription']);
$subscription_items = $subscription->get_items();

What I am trying to do is allow users to update quantities of their product. So If they update quantity I want to update the subscription's item quantity so that future orders are generated with updated quantity. I saw there is update_product method in WC_Abstract_Order class. I think this can be used but I am confused on this note in comments:

* Update a line item for the order.
*
* Note this does not update order totals.

Do I need to recalculate totals when I use this? Also I needed to remove line item when quantity was 0. Is that possible?

As I do not see a remove item method.

Thanks

So I was able to make this work doing following.

1. Remove all order items from subscription object.
2. Run through the $_POST to get changed quantity
3. Add product to subscription again.

note: I am using custom field price_level as it was dynamically priced during subscription and we wanted to use it so that price was same as when they subscribed.

    //remove product items
    $subscription->remove_order_items('line_item');
    //add product item again
    foreach($_POST['quantity'] as $product_id => $qty) {
        if($qty > 0) {
            //we will need to set dynamic prices based on cusotm field
            $price_level = get_field('coffee_price_level', $subscription->id);
            //Get the product
            $product = wc_get_product($product_id);
            //set the price
            $product->set_price(floatval($price_level));
            $tax = ($product->get_price_including_tax()-$product->get_price_excluding_tax())*$qty;
            //subscription item price level
            $subscription->add_product($product, $qty, array(
                'totals' => array(
                    'subtotal'     => $product->get_price(),
                    'subtotal_tax' => $tax,
                    'total'        => $product->get_price(),
                    'tax'          => $tax,
                    'tax_data'     => array( 'subtotal' => array(1=>$tax), 'total' => array(1=>$tax) )
                )
            ));
        }
    }