The two proposals a Solution Architect should recommend to track adoption of migrated functionality from Classic to Lightning are:
1. Track Adoption Rates within the Lightning Usage, and monitor a change in metrics within existing reports and dashboards. C. Provide the CIO a list of the User Stories around the new functionality and the Gap Analysis done between Classic and Lightning.
Tracking adoption rates and success metrics is one of the best practices for driving Lightning Experience adoption, as it allows UC to measure how well users are using the migrated functionality and identify areas of improvement or feedback. According to 2, monitoring a change in metrics within existing reports and dashboards can also help UC evaluate the impact of Lightning Experience on their business performance and user satisfaction.
Providing a list of user stories around the new functionality can help UC communicate the benefits and value of Lightning Experience to their users and stakeholders, as well as align their expectations and goals with the migration project. According to 3, providing a gap analysis done between Classic and Lightning can also help UC understand what features or customizations are available or not available in Lightning Experience, as well as plan for any necessary changes or enhancements.
https://trailhead.salesforce.com/content/learn/modules/lex_migration_rollout/lex_migration_rollout_enabling

Option C seems correct because it is important to document all the customizations added to the system, such as code, configuration, integrations, etc., so that they can be easily understood, maintained, and updated by the support team or future developers.
Option D seems correct because it is essential to communicate and train users on new features that are rolled out to support UC's business needs and goals. This can help users adopt the new features faster and more effectively, as well as reduce confusion or frustration.
Option E seems correct because it is advisable to have separate environments for development, training, and production purposes. This can help ensure that new features are developed and tested in a safe and isolated environment before being deployed to the production environment where they can affect real users and data.

This option would follow the lead-to-invoice process that Salesforce Billing supports2, which involves creating an invoice from an order and then sending it to the ERP system for payment processing. This option would also leverage Revenue Cloud and Sales Cloud features such as CPQ and Billing to automate and streamline the quoting and invoicing process.
Since UC's CRP will be the system of record for invoices, the order information will need to be passed to the back-office ERP for invoice creation and processing. Therefore, the business process should include Lead, Opportunity, Quote, Order, and then directly into the back-office ERP system. Payment processing can be handled within the back-office system or potentially integrated back into Salesforce with appropriate consideration for data security and compliance.

https://help.salesforce.com/s/articleView?id=sf.icx_b2b_cart_to_quote_connector.htm&language=en_US&type=5 According to 1, the connector lets you sync simple products with a flat price between CPQ and B2B Commerce. However, it does not support syncing complex CPQ bundles, such as nested bundles or option constraints. You need to use custom code or a third-party solution to sync complex bundles.