How Do Book Editing Companies Shape a Manuscript’s Journey?

At a local author gathering, someone shared how Houston Book Publisher recommended a reliable book editing company to refine their manuscript. The author described how structural edits, clarity improvements, and stylistic guidance transformed their story. It made me curious do these companies simply polish text, or do they play a deeper role in shaping the narrative and tone? How much influence should a book editing company have on an author’s original vision while still preserving their voice?