I run both iOS' Photos app as well as the Google Photos app on my iPhone, but I worry that doing this causes two copies of each picture to be stored on my phone. Does it, or do the apps share the photos they both show me?
I have an iPhone 6 running iOS 11.
Please note that this question is only about storage on the phone. What happens in the cloud as regards Google Drive and iCloud is not part of my question. In case it happens to be relevant, both apps back up my photos to their respective clouds.