Once your custom fields are created and configured, create your custom report type. 

Go to Setup > in the Quick Find box, enter Report types > open it

Click on New Custom Report Type

Fill in the builder.

Primary Object: Opportunities

Enter Label (Opportunities with/without ClosePlan) and Name (Name will auto enter) and the Description.

Store in Category: Opportunities

Deployment Status: Deployed 

Click Next.

Click on ('Click to relate another object')

Use the dropdown to select ClosePlan and tick “A” records may or may not have related “B” records and Save.

Once you have created your custom report type, you have the ability to edit the naming conventions used for different fields. 

To edit the naming conventions, select edit layout. 

Select a field > Edit Properties.

Change the display name > Ok

Your field will now display your modified convention on your report.