Hi there @Bookish ,
For syncing Scrivener desktop to Scrivener desktop, Google Drive is not a good choice for a syncing service. See this recent thread for a typical example of what can happen. Also, see this advisory from L&L.
For syncing Scrivener desktop to iOS Scriv, my understanding is that Google Drive does not provide the low level API/programming hooks needed for syncing iOS Scrivener. Dropbox does, which is why Dropbox is currently the only syncing service supported by iOS Scriv. See this explanation from L&L for a bit more detail.
Best,
Jim