For optimal performance and data access control, the Solution Architect should:
A) Use profiles and/or permission sets to give View All access to Customer Service on the Contact object. This allows Customer Service to access the necessary contact information while maintaining the principle of least privilege.
D) For each Account, assign Sales Contacts to the Sales team and all the rest to a Customer Service representative assigned to the Account. This approach ensures that each team has access to the relevant contacts while keeping private information secure and maintaining system performance by minimizing complex sharing rules.
Salesforce's documentation on sharing and visibility best practices recommends such strategies to manage access to records efficiently and securely.
https://trailhead.salesforce.com/en/credentials/sharingandvisibilityarchitect

In Universal Containers' architecture, Salesforce serves as the System of Record (SOR) for sales data such as Opportunities and Quotes, centralizing sales activities and data management. Orders, once confirmed, transition to the ERP system, where they are processed and fulfilled, making the ERP the SOR for order, invoice, and payment data. This delineation ensures clear data ownership and process efficiency, with Salesforce facilitating customer engagement and sales processes, and the ERP managing financial transactions and fulfillment, in line with best practices for leveraging Salesforce in a multi-system environment.

governance is the process of defining and enforcing policies, standards, and best practices for managing your Salesforce implementation. It helps you ensure quality, consistency, security, and compliance across your multi-cloud solution.
https://trailheadacademy.salesforce.com/classes/arc801-Design-and-implement-b2b-multi-cloud-solutions

Data migration is the process of transferring data from one system to another1.
Data migration in Salesforce requires careful planning, preparation, and execution234.
Data migration best practices include setting up a data governance plan, focusing on data quality, creating templates, verifying proper transfer, and using appropriate tools2356.

CPQ B2B Commerce Connector is a tool that synchronizes data from CPQ product and pricing objects to B2B Commerce objects1.
CPQ uses discount schedules and B2B Commerce uses tiered pricing to handle volume-based pricing23.
The connector does not support mapping tiered pricing to discount schedules out of the box23.
The connector uses pricing from B2B Commerce to define the pricing on the generated quote lines by setting their Special Price fields4.