In Nation theme we pre-defined USD as default currency. You can add/edit the currency for your shop in this page http://DOMAIN/admin/commerce/config/currencies
In Nation theme we pre-defined Nation Shop as default store. You can add/edit the currency for your shop in this page http://DOMAIN/admin/commerce/config/stores
Product Type and Product Variations Type
In Nation theme, we are using the default Product Type and Product Variation Type which are generated when installing the commerce module.
You can check details settings for these type here http://DOMAIN/admin/commerce/config/product-types and http://DOMAIN/admin/commerce/config/product-variation-types
In Nation theme, we added "Paypal Express Checkout" method for testing purpose, you can add your own payment gateway method in this page http://DOMAIN/admin/commerce/config/payment-gateways
This feature will be used to add the custom product attributes. For example, Size, color...
In Nation theme we added a custom attribute called Size. You can add/edit the product attribute in this page http://DOMAIN/admin/commerce/product-attributes