prompts will give very different results. this is where you do the work.
A good editor could probably reduce all LLM outputs on a subject down to the same point.
Nope, if you provide pages and pages of example of a style to imitate, it will do it and do it fairly well. Of course how well they do it differs from one model to the next, but providing context and extensive system prompt does change things every time.
Yet another reason why the future is open weight.
Not my experience.