WooCommerce, Settings, Split Order, Rules: labels dropship from a supplier with prices hidden, bulky items go to freight.
Each line goes to the first rule it matches. Lines of the same rule become one order. Lines that match no rule stay on the original.
Conditions: shipping class, category, tag, product or SKU, attribute, vendor (product author, for marketplaces), product field (for stock location plugins) and on backorder.
Rules run right after payment, before the backorder split, and from Bulk actions on the orders list.
Each rule can set the status of its order and email it to a supplier or warehouse.
The supplier email: only the rule’s items, SKUs and the shipping address. Prices are hidden when the rule says so.