Which component is more medial: the right lung or the tracheal bifurcation?

The more medial is the tracheal bifurcation.

In anatomy, we refer that structure is more medial than other when it's closer to the median plane which is in the midline of the body, that divides the body into left and right. The trachea its "crossed" by that imaginary line, while both lungs are more to the sides.