Open Viewing options → Video in the player. The preview groups picture adjustments in one panel so you can see the result while watching.
- Start with a preset such as Cinema, Vivid or Dark room.
- Fine-tune Brightness, Contrast and Saturation. Gamma, Hue and Sharpness are also available.
- Use Picture fit, Zoom or Rotation to change how the image sits in the player.
- Use Reset when you want to reset adjustments.

For picture and decoding defaults, open Settings → Picture. This includes HDR tone-mapping strength and hardware decoding.
Casting and 10-bit HDR are CnX Pro features, with a free trial on every video. Check the app for the options available to you.