For a client implementing CRM Analytics with a variety of user roles, creating and assigning Salesforce permission sets is the most flexible and scalable solution. Here's why:
Flexibility and Customization: Permission sets allow for specific access rights to be compiled and assigned based on user roles without altering their existing profiles.
Scalability: As the organization grows or roles change, permission sets can be easily adjusted or reassigned to accommodate new requirements or users.
Simplified Management: Managing access via permission sets simplifies the administration of user rights, making it easier to ensure that each group has the appropriate level of access.

Reference:
https://trailhead.salesforce.com/en/content/learn/modules/wave_analytics_templates_intro/wave_analytics_templates_in_action

In Salesforce CRM Analytics, when dealing with multi-currency environments, the system relies on the organization's corporate currency setting for reporting, unless explicitly overridden. In this case, even though the Opportunity data is stored in GBP in Salesforce, the dashboards are showing USD because the corporate currency for the org is set to USD. This behavior is expected unless currency conversion logic is implemented in the datasets or recipes.
The corporate currency serves as the default for currency fields in datasets and dashboards unless configured otherwise. This can be confirmed under the "Manage Currencies" settings in Salesforce.