The official Google Drive app keeps everything on your startup disk. Gocci puts Google Drive in Finder and keeps what you download on whichever disk you choose, an external one included. Built on File Provider, the same mechanism as iCloud Drive: opening a folder downloads nothing, thumbnails don't pull files, reading part of a 70GB video fetches only that part, and Finder's own cloud badges and Remove Download just work. rclone runs underneath, no kernel extension. Free and open source.