Explanation
Mass Order pricing is done via a batch job, which means that the prices are not calculated in real time, but rather at a scheduled time. Mass order works with the variation product, which is a product that has multiple SKUs with different attributes, such as size or color. Mass order does not work with the default wishlists, which are used to store products that the customer wants to buy later. Mass order is not mobileready with the ccrz templates, which are the default templates for the storefront pages. Salesforce References: B2B Commerce Developer Guide: Mass Order, B2B Commerce Developer Guide: Variation Products

Explanation
One way of preventing an existing payment page from being shown on the checkout payment page is to remove the payment type associated with the payment page from CO.pmts, then rebuild and activate a new cache. This will exclude the payment type from the list of available payment options on the checkout page.
The other options are either not feasible or not effective in hiding the payment page. Salesforce References: B2B Commerce and D2C Commerce Developer Guide, Payment Configuration Settings

Explanation
Salesforce B2B Commerce API sizing blocks can support multiple API sizing requests in three ways:
* When different entities are specified in the method invocation. For
example, ccrz.ccServiceProduct.getProducts(ccrz.ccAPI.SZ_M, ccrz.ccAPI.SZ_L) will use the SZ_M sizing block for the product entity and the SZ_L sizing block for the related entities.
* SZ_ASSC is used. This flag indicates that the associated entities should use the same sizing block as the primary entity. For example, ccrz.ccServiceProduct.getProducts(ccrz.ccAPI.SZ_M, ccrz.ccAPI.SZ_ASSC) will use the SZ_M sizing block for both the product entity and the related entities.
* SZ_ASSC is not used. This flag indicates that the associated entities should use the default sizing block, which is SZ_M, unless otherwise specified. For example, ccrz.ccServiceProduct.getProducts(ccrz.ccAPI.SZ_M) will use the SZ_M sizing block for the product entity and the SZ_M sizing block for the related entities. Salesforce References: B2B Commerce and D2C Commerce Developer Guide, Data Sizing Conventions

To check user permissions in Lightning web components, a developer should import two scoped modules: @salesforce/permission and @salesforce/customPermission. The @salesforce/permission module allows the developer to check if the user has access to a standard permission, such as View Setup or Modify All Data. The @salesforce/customPermission module allows the developer to check if the user has access to a custom permission, such as Enable Debug Mode or Manage Orders. The other modules do not exist or are not related to user permissions. Salesforce Reference: Lightning Web Components Developer Guide: Check User Permissions, Lightning Web Components Developer Guide: Import Salesforce Modules