A https://www.freecram.com/question/Salesforce.Nonprofit-Cloud-Consultant.v2021-01-10.q37/a-nonprofit-organization-has-been-using-salesforce-without-npsp-the-organization-is-now-interested-in ((see in comments)

To evaluate and recommend whether to use NPSP in the same Salesforce environment or start over in a new environment, the consultant should use Salesforce Optimizer. Salesforce Optimizer provides a comprehensive report that evaluates the current Salesforce org and identifies areas for improvement and optimization.

Log in to Salesforce: Access the Salesforce org.

Navigate to Salesforce Optimizer: Go to Setup, search for "Optimizer", and select "Salesforce Optimizer".

Run Salesforce Optimizer:

Click "Run Optimizer".

Wait for the evaluation to complete. Salesforce Optimizer will generate a detailed report.

Review the Report:

Analyze the report to understand the current state of the Salesforce environment.

Look for insights related to customizations, data quality, and system usage.

Make a Recommendation:

Based on the findings, determine if the existing environment is suitable for implementing NPSP.

If significant issues or customizations are found, consider starting over in a new environment.

Using Salesforce Optimizer helps ensure an informed decision based on the health and suitability of the current Salesforce environment.