Should I Keep the .json Files After Fixing My Photos?
Once the dates are inside your photos, the .json files have done their job. When to delete them and when to hold on.
Once the date and location are written into the photo, the .json file is no longer needed. The photo carries its own metadata, the way a photo from a camera does. Every app can read it without help.
Keep them until you have checked the results. Open a few photos and confirm the date is right. If something went wrong, the .json files are the only copy of the original information, and they cannot be recovered once deleted.
Takeout JSON Metadata Fixer can tidy them up for you after a clean run, or leave them alone if you prefer. It shows you what it changed before you commit to anything. Free for your first 500 photos.