My eye line is between the top bezel and the middle of my main monitor (so about 3/4 the way up) .. I find it kinda depends how far away you sit from your monitors as well.
Last ergonomic human resources check up (when I worked in an office) once told me that because its less effort and you have more freedom of movement for the head to tilt down than up its the ideal location .. but its what feel best to you and wont destroy your neck and posture over time.
Here is my monitor setup if it helps
The top one is mainly for choosing my next Spotify track or having YouTube build videos on when I am working. The two side monitors are for portrait views of my code.
The desk height is aligned with me sitting up straight and 90 degree angles at the elbows, feet resting on the floor, knees at 90 degree angles.