I disagree with one bit. We always have our boards as public as possible. I think one of the main selling points of following a product backlog is the visibility it grants to stakeholders. You can point to stories in the queue and what acceptance criteria was agreed to. And they can see and adjust the priority order of tasks to be done. And see when stories are in a demo-ready state.

Estimates are an interesting one. The theory of story point estimation is that you are estimating the size of the work being and not even implying, let along guaranteeing any notion of timing. That being said, it's still sometimes a valid question to ask why something is taking so long.