Can I work on iMovie online?: ie upload a library to googledrive or etc and work on it from any Mac?
I'd recommend Dropbox. You'd be able to edit files locally with Dropbox, and then it would handle syncing them to the cloud. You'd just have to make sure you left your computer on long enough to allow it to finish syncing after you made changes.

I'm unsure if Google Drive works the same way - but I use Dropbox for something very similar to your scenario and it works great. I can edit files at home or at the office, and they sync across so I don't have to worry about transporting things back and forth.