How can I configure Bold Upsell to offer two free products when a customer's cart value reaches a certain price?
You can use the funnel feature in Bold Upsell to offer the first product for free. Once the first product has been accepted, you can then present another product for free within the same popup.
More details on using funnels can be found here - https://support.boldcommerce.com/hc/en-us/articles/360045467711-Upsell-Funnels.