Bloomkeeper works at the level of involvement you choose. You set this during setup and can change it at any time from Settings.
Start on Guided Approval. Watch what it suggests for a week or two. Once you can see the pattern of what it wants to do and you are comfortable with the quality, move up.
There is no wrong answer here and no penalty for changing your mind. Plenty of shops stay on Guided Approval permanently because they like reading everything first.
Auto is not instant. On a large site with a lot of suburbs and products, creating, reviewing and publishing everything can take several days or even weeks. It works steadily in the background rather than all at once. This is deliberate: it keeps the work reviewable and stops a large batch of changes landing on your site in one go.
Whatever mode you choose, everything is logged. Nothing happens silently, and you can always see what was done and when under History.