Explanation
The tool that would help UC understand the existing functionality of all of its reporting tools is a capability model. A capability model is a visual representation of the core capabilities or functions that an organization performs or delivers to achieve its strategic objectives. A capability model helps to identify and organize high-level process areas that span across different departments or teams, as well as highlight any gaps or overlaps in functionality. A capability model can also help to prioritize and scope Salesforce projects based on business value and impact.
In this case, UC can use a capability model to map out all of its reporting tools by their capabilities or functions, such as data sources, data integration, data analysis, data visualization, data sharing, etc. This would help UC understand what each reporting tool can do or provide, how they relate or differ from each other, and where there may be redundancies or inefficiencies in their reporting processes. References:
https://trailhead.salesforce.com/content/learn/modules/salesforce-business-analyst-certification-prep/business-pro

Explanation
The type of process diagram that the business analyst should use at the beginning of a Salesforce project to outline high-level process areas such as "Prospect to Contract" is a capability model. A capability model is a visual representation of the core capabilities or functions that an organization performs or delivers to achieve its strategic objectives. A capability model helps to identify and organize high-level process areas that span across different departments or teams, as well as highlight any gaps or overlaps in functionality. A capability model can also help to prioritize and scope Salesforce projects based on business value and impact.
References:
https://trailhead.salesforce.com/content/learn/modules/salesforce-business-analyst-certification-prep/business-pro

This answer provides an example of how to construct the user story for creating a new picklist field called
"Lost Reason" on the Opportunity object with the goal of improving pipeline reports, using this format: As a
<persona>, I want <goal>, so that <value>. This answer defines the persona as "sales leader", who is likely to be one of the main users or beneficiaries of this feature. It also defines the goal as "see more details on Closed/Lost Opportunities", which is what they want to accomplish with this feature. Finally, it defines the value as "help the sales team improve close rates", which is why they want to accomplish this goal and how they will measure success. References:
https://trailhead.salesforce.com/en/content/learn/modules/salesforce-business-analyst-quick-look/use-user-stories

The best practice to establish benchmarks to evaluate existing processes is to show tangible impact from changes to processes. Benchmarks are quantifiable measures that can be used to compare current performance with desired performance or best practices. They can help CK evaluate how effective its sales processes are, identify gaps or opportunities for improvement, and measure the results or benefits of process changes.
Proving processes are out of date and require a new solution is not a best practice, but a potential outcome of benchmarking. Comparing processes against CK's closest competitors is not a best practice, but a possible source of benchmarking data. References:
https://trailhead.salesforce.com/content/learn/modules/salesforce-business-analyst-certification-prep/business-pro
https://trailhead.salesforce.com/content/learn/modules/salesforce-business-analyst-certification-prep/user-accepta