If your video was recorded in a noisy environment, Captions can easily separate the vocal track from the background track easily, making your video sound as though it was recorded in a professional studio. Denoise can remove echo, wind, crowd noise, and other background sounds, which means you can easily fix it in post.
It is not possible to control how much denoise you apply. Captions will automatically remove the necessary amount of background noise to ensure your vocals sound great.