Picture printing

When you download photos or anything else to any computer it lands somewhere in the computer, to an application. You may be downloading them to a Finder window, Finder is an applications. Your Mac came pre-installed with the Photos application located where all of your apps are located in the Applications folder. You even have icon of it in the Dock that looks like

The is the application that Apple uses for storing, managing, editing and yes printing photos. To learn how to use it please refer to https://support.apple.com/guide/photos/welcome/mac

You have not provided much in the way of useful information. We need to know which app you are move the iPhone's photos to on the iMac. If the photos go from the iPhone to the Photo's app on the iMac they are most certainly editable.

Harvey,

Please re-read my first post and answer the question of when you import a photo onto your iMac which iMac app do the photos reside in?