Here's my workflow for GDocs:
Begin project. Private project, no one is messing with a thing and they can't see what I'm doing because I haven't shared it.
Send first submission. This can be done a couple of different ways. 1. Just download the file as a docx file and send it to them. They don't have to know it was written on GDocs. 2. Initiate sharing as a link. This means anyone with the link can do anything you let them do. So, for me, I would allow them to view and comment, but not change. If they want to make changes they can download the file and make their changes in Word and send it to me.This is handy when you are writing something like a white paper that will have designers and illustrators involved. You don't have to know them or get involved with that. Just send them a link and let the marketing director be the project manager. Finally, for one editor that I love, I just share it through her GDoc account. She can do what she wants with it because she paid for it already.
Why I like GDocs.
1. Easy to work on stuff in my spare time. I don't Upwork full time, so when I have a little bit of time and access to a computer, I can keep working.
2. Permanent revision history. I had a client make a bunch of changes and then accidentally delete something they wanted back. I just jumped into the revision history, made a copy, and sent them the file. No fuss. took all of 3min and I could've done it from any computer.
The security risk is on you, not on GDocs. If your password sucks then your security sucks. If you start sharing folders and don't have things compartmentalized, then that's on you too. GDocs can be as safe as you are.
But you don't have to worry about people watching over your shoulder unless you share your rough draft with them at the very start. If you do that, then I would suggest you go back and read Stephen King's "On Writing" again. He tells you that the rough draft is written with the door closed, and every other draft is written with the door open :-)