Google drive making extra local copy on phone
Some possible causes to why the Drive app saves local copies:


The file has been accessed recently and cached. This is possibly to reduce more bandwidth usage when the file is accessed regularly. Clearing the cache from the in-app's Settings can save some space, including limiting the cache size to a minimum of 100 MB.
The file is marked as "available offline". Files that are marked as "available offline" will be automatically downloaded to the local disk. To toggle it, tap the overflow context menu (3 vertical dots) on the file, and select "Available offline". To check which files are marked as such, there's an "Offline" category on the navigation drawer.