Picture styles/presets such as Portrait or Landscape generally do not change the underlying RAW sensor data. They do affect files the camera processes in-camera, especially JPEGs and typically video.

However, those settings can still matter when shooting RAW because the camera usually uses a JPEG preview based on the selected picture style for the rear screen, histogram, and highlight warnings. If you raise contrast or sharpness a lot, the preview may make the image look harsher or more clipped than the RAW data really is. Using a lower-contrast style can therefore give a more conservative, useful preview when exposing RAW stills.

For JPEG shooting, these settings directly affect the final file, so choosing lower sharpness/contrast can leave more room for later editing if that matches your workflow.

For video, the advice to reduce contrast is more important because most video is recorded in a processed format rather than RAW. Lower-contrast settings can help preserve highlight and shadow detail for grading later.

So: RAW files themselves are generally unaffected, but the preview and exposure aids are affected; JPEGs and most video are affected directly.