A Flow is a scalable way to set the legal entity on the order product and order product consumption schedulebecause it allows you to automate complex business logic without writing code. A Flow can be triggered when a record is created and run before the record is saved, which means that you can assign the legal entity to the order product and order product consumption schedule before they are inserted into the database. This way, you can ensure that the order product and order product consumption schedule have the correct legal entity for the billing, tax, and revenue recognition treatments that are applied to them. A Flow also gives you more flexibility and control over the logic and criteria for setting the legal entity, compared to a workflow or a custom setting. A Quote Calculator Plugin (QCP) is not a scalable way to set the legal entity on the order productand order product consumption schedule because it is a custom code solution that requires development and maintenance. A QCP also runs after the order product and order product consumption schedule are created, which means that you have to update the legal entity after the record is saved, which can cause data validation issues. A workflow or a custom setting are also not scalable ways to set the legal entity on the order product and order product consumption schedule because they have limitations and drawbacks, such as:
A workflow can only run after the record is created and saved, which means that you have to update the legal entity after the record is saved, which can cause data validation issues.
A workflow can only execute simple logic and actions, such as field updates, email alerts, tasks, and outbound messages. It cannot perform complex logic or actions, such as loops, conditions, variables, or invocations of other processes or services.
A custom setting is a type of custom metadata that stores datathat can be accessed by formulas, validation rules, flows, Apex, and the SOAP API. However, a custom setting is not a good way to store data that changes frequently or varies by user or profile, such as the legal entity. A custom setting also requires manual configuration and maintenance, which can be error-prone and time-consuming. References:
Legal Entities
Automation Guidelines for Orders and Order Products
Flow Builder
Burundi 
Venezuela 