Explanation
To enable a new payment type for the Checkout flow, three possible configuration metadata descriptors are needed:
* *.pay: This descriptor defines the payment type name, label, description, icon, and handler class. For example, CO.pmts.CreditCard.pay defines the payment type for credit card payments.
* *.Edit: This descriptor defines the Visualforce page that is used to edit or update an existing payment of this type. For example, CO.pmts.CreditCard.Edit defines the page that allows editing a credit card payment.
* *.New: This descriptor defines the Visualforce page that is used to create a new payment of this type.
For example, CO.pmts.CreditCard.New defines the page that allows creating a new credit card payment.
Salesforce References: B2B Commerce and D2C Commerce Developer Guide, Payment Configuration Settings

You should avoid using ccLog in two scenarios. First, you should avoid using ccLog with System.LoggingLevel.ERROR when passing in a method invocation as the third parameter, such as ccrz.ccLog.log(System.LoggingLevel.ERROR, 'D:something', myCallToGetMessage(pl) ). This is because if an exception occurs within the method invocation, it will not be caught by ccLog and will cause an unhandled exception on the page. Instead, you should use a try-catch block around the method invocation and log the exception separately. Second, you should avoid using ccLog with System.LoggingLevel.DEBUG when passing in a large collection or object as the third parameter, such as ccrz.ccLog.log(System.LoggingLevel.DEBUG, 'D:myOrderList', myOrderList), where myOrderList is a list of orders. This is because logging large objects can cause performance issues and consume a lot of heap space. Instead, you should use a loop to log only the relevant fields or properties of the object or collection. You can use ccLog with System.LoggingLevel.WARN when passing in a string as the third parameter, such as ccrz.ccLog.log(System.LoggingLevel.WARN, 'D:something', 'Something unexpected occurred: The data we were expecting for pl was not there,'). This is a valid use case for logging a warning message. You can also use ccLog with System.LoggingLevel.DEBUG when passing in a small object as the third parameter, such as ccrz.ccLog.log(System.LoggingLevel.DEBUG, 'D:myOrder', myOrder), where myOrder is an order object. This is acceptable as long as the object is not too large or complex. Salesforce Reference: [B2B Commerce Developer Guide: Logging]

Three steps that are necessary to have a subscriber page added to Salesforce B2B Commerce after creating a custom Visualforce page are:
Create a new CC Subscriber Page record that points to your custom Visualforce page. This record will store information about the subscriber page, such as the name, description, URL, and Visualforce page. For example, you can create a new record named MySubscriberPage that points to your custom Visualforce page named MyPage.
Refresh the Page Keys Index in CC Admin. This action will update the page keys index, which is a cache that stores the mapping between the page keys and the subscriber pages. You need to do this whenever you create or modify a subscriber page record.
Enable the Subscriber Page in CC Admin. This action will allow you to select the subscriber page from the CC Page Settings configuration and assign it to a CC Page. For example, you can enable MySubscriberPage and assign it to the Home page. Salesforce Reference: B2B Commerce and D2C Commerce Developer Guide, Subscriber Pages

Explanation
The templating, JavaScript, and CSS frameworks that the cloudcraze managed package leverages are Bootstrap, Backbone.js, and Handlebars.js. Bootstrap is a CSS framework that provides responsive design and layout components. Backbone.js is a JavaScript framework that provides models, views, collections, and events for building single-page applications. Handlebars.js is a templating engine that allows generating HTML from JSON data. Salesforce References: B2B Commerce and D2C Commerce Developer Guide, Front-End Development