When you upload, scan or improve photos using Reimagine, they are saved in photo albums that are always private by default.
When you sign in to Reimagine using your MyHeritage account credentials and upload your photos to an album you previously created on your MyHeritage family site, the privacy settings for those photos will depend on the album’s settings. Any content you upload to Reimagine will be visible on that same family site on MyHeritage. That means that any member of that family site on MyHeritage can view the content you added via Reimagine.
You can log in to your MyHeritage account online and check your albums' privacy settings by clicking on your name in the top-right corner and selecting 'My privacy'. On the privacy page, click on 'Content' on the left-hand menu to see the privacy options for your photos.