https://www.salesforce.com/products/marketing-cloud/faq/

When a nonprofit organization creates a custom Opportunity name for all organization donations, the consultant should discuss the following considerations:
Using the "Refresh Name" Action (B):
The organization should use the "Refresh Name" action to change existing Opportunities to the new naming convention. This action ensures that the custom naming convention is applied correctly.
Navigate to the Opportunity record.
Click on the "Refresh Name" button to update the Opportunity name according to the new naming convention.
Using the "Refresh All Opportunity Names" Button in Bulk Data Processes (C):
For bulk updates, the organization should use the "Refresh All Opportunity Names" button available in Bulk Data Processes.
Go to NPSP Settings.
Under Bulk Data Processes, find the "Refresh All Opportunity Names" button.
Click on it to update all existing Opportunities to the new naming convention in bulk.
These methods ensure that the custom naming convention is applied consistently across all existing Opportunity records, maintaining data integrity and consistency within the Salesforce org.

To track a check that includes donations from several donors for a specific program, the consultant should configure GAU Allocations and Partial Soft Credits in NPSP. Here's why:
GAU Allocations:
General Accounting Unit (GAU) Allocations are used to track how donations are allocated across different programs or funds.
This feature allows the nonprofit to specify which portion of the check is designated for the specific program, providing clear tracking and reporting.
Partial Soft Credits:
Partial Soft Credits can be used to attribute portions of a single donation to multiple donors.
This feature allows the nonprofit to recognize each donor for their contribution while keeping the accounting of the total donation intact.
Reference:
Salesforce NPSP Documentation on GAU Allocations
Salesforce NPSP Documentation on Soft Credits