Hi @aidanw,
What part of a users eyes does the Magic Leap 2 track?
To see what part of the eye is visible to the Magic Leap 2, please check out this post: Obtain Eye Camera Images (Example) Unity
How does the shape of a users eyes and the colour of their iris affect tracking?
Irregular eye shapes can affect eye tracking accuracy, but since the eye images are grayscale, iris color doesn't have an impact on the tracking quality.