each of those profiles are available at the same time, but are sandboxed from each other?

Correct. For the three special profiles, they're all active at the same time, you can use them like you would any other app. They're just isolated from each other.

Gos also has other user profiles, where you have to swipe down and swap users, those are more cumbersome, but more isolated. But for daily driving, you have three profiles you can use simultaneously, at the same time, no login, no log out, and they're isolated from each other

For instance, you can have two versions of WhatsApp running at the same time, one in each profile, and they can't see each other, but you can swap between them like any other two apps.