You cant 'peak' 'thicken' 'lengthen' or change in any way the shape of your biceps. Its genetic.
by doing hammer curls, zottoman curls,and neutral and overgrip pulling movements, you incorporate the brachialis muscle more, and this is the principle muscle in the upper forearm that gives the 'thick' look to the arm.
The bicep is not just an elbow flexor, it is also a principle supinator of the hand. by doing dumbell curls from neutral at the bottom, twisting to palm up at the top, you pretty much maximise bicep engagement in your curls. Dont use so much weight that the twist is just a 'flick' using momentum, actually put concentrated force into the rotation of the wrist finishing in a hard squeeze at the top.
You cant really do more for your biceps than that. The rest is down to your genetics.