For 1, effectiveness still depends on the size and complexity of the codebase.

From my experience, as complexity and size grow, each prompt takes longer, does less, and is prone to more mistakes and disruptions to other parts of the codebase.

The code base I work on is > 30 million lines (excluding comments and blank lines) and most (but not all) of the people on the team are finding it pretty effective. That doesn't mean it wouldn't be more effective on a smaller code base.