The saving is based on what is in the cart now. Product prices at the time the shopper checks out are used, not the prices when you created the bundle.
Price Override — the shopper pays the override for the bundle's lines, as long as those lines add up to more than it.
Percentage / Fixed — taken off the current total of the bundle's lines.
Inactive or deleted bundle — lines already in a cart lose the saving and go back to normal prices.
No bundle stock. Availability depends on each product's stock. Keep enough of every item for the bundles you promote.
Variants. Bundles use the products as added. If a product has sizes or colours, consider whether the shopper needs to choose one; bundles are best with products that have no options.