Difference between Single SKU and Multiple SKU Build Box
Single SKU Build Box:-
The bundle product appears as a single product (with a single SKU) in the cart, Orders section, and Order emails. Each bundle sale's items are listed as 'line item properties.'
1. It has a unique SKU for their bundle item.
2. If you are using any 3rd party apps to fulfill your own orders then this feature will not work.
3. It does not track the inventory so you need to manage the stock manually.
Multiple SKU Build Box:-
The bundle is split into different products (each with its own SKUs) that will be displayed as such in the cart, Orders section, and Order emails.
1. It's compatible with 3rd party fulfillment app.
2. Build box transfer the bundle order data to 3rd party apps.
3. It tracks the inventory because the product uses its original SKU in order.