When fetching the rates for shipping fees, there are different flows that can lead to the selection of a particular label. The flags that interact to bring you the rates are dynamic_shipping_rates and direct_shipping_rates. Due to the interaction of these two flags, 4 distinct possibilities arise.
dynamic_shipping_rates is on || direct_shipping_rates is off
In this case, you will have to configure your carriers, zones, facilities, and lanes to provide your shoppers with the rates for shipping. The rates visible to the shoppers will be the rates you have configured in the settings mentioned above. If you decide to charge different amounts on Returns and Exchanges, you can configure them in the Shipping Methods screen.
dynamic_shipping_rates is off || direct_shipping_rates is on
In this case, the rates that your shoppers will see will come directly via the carrier (via EasyPost). You will not be able to charge different amounts for returns and exchanges. However, if you want to waive the shipping fee for exchanges as an incentive, you can do so by turning on the waive_exchange_fee flag.
dynamic_shipping_rates is on || direct_shipping_rates is on
In this case, the system will make use of the configurations you have done in carriers, zones, facilities, and lanes as a way of determining which areas to serve, and the shipping rates that the shopper will see will come directly via the carrier (via EasyPost)
dynamic_shipping_rates is off || direct_shipping_rates is off
In this case, the amounts you have mentioned in the Shipping method, for returns and exchanges will be charged to the shopper.