If you want to set the camera to match the user's height, assuming they're standing in the room ("room scale"), you want to:

  • Set the XRRig's Y to 0 so it's on the floor.
  • In the Camera Offset component, set Requested Tracking Mode to Floor and Camera Y Offset to 0.

For other options, see https://docs.unity3d.com/Manual/configuring-project-for-xr.html.