Moving files to new HD and how Time Machine manages

I keep my photo images on an external 6 TB HD. The drive is now 5 years old and I'm getting nervous about its reliability. I use Time Machine to backup this drive. I have purchased a new larger external 8 TB HD to store my photos. After I copy/move the photos from the old to the new external HD what will Time Machine do? Will it do a full copy of the new drive or only copy when changes are made in the future to data on the new HD? My Time Machine is a 10 TB drive that is about 70% full. Previous discussions on this topic are more than 10 years old, have things changed with Time Machine?