Shipping services you can can offer the customer on Walmart Marketplace are generically named:
You can map these services to real shipping methods, i.e. Standard = USPS Priority. When this is done, all "Standard" orders will change to "USPS Priority" as the selected service.
You can also mark services as "Rush Orders" i.e. OneDay = FedEx Standard Overnight and marked as Rush. With Rush Orders, the service selected on the order takes precedence over a service selected on the product level.