Biceps peak and shape is determined by the length of the muscle's tendon.
Long tendons means a short biceps with high peak.
Short tendons means a long, more stretched-out biceps with low peak.
These tendon variations have little to no influence on performance, just aesthetics. And since tendon lengths can't be changed through training, biceps peak (and overall shape) is mainly genetics. That doesn't mean we can't add some serious mass to it though