Incline DB with wrist relaxed back and supinating hard for the peak contraction is my favorite.I love/hate the burn.Same technique in drag curl just doesn't hurt the same for me.Use them both,just in different workouts.Don't forget hammer curls to build brachialis as it pushes the bicep up.
I tend to overthink things. It’s the OCD taking over. So what your saying is standing dumbbell curls will produce the same results and incline dumbbell curls.
There is no way to increase the peak because is completely genetic and no way to target the long head?
The main thing on curls is to not move your upper arm much, keep it stationary. Keeping it in a way stuck to your side and not letting the elbow come up. Once you start moving the upper arm up then you bring in front delt to assist the curl and probably some other muscles assist too. That is why I like doing incline curls because you let your arms hang down and it makes it harder to cheat the weight up with your delts. Easier to keep the movement strict.
One of my most favorites for biceps is the basic standing alternating dumbbell bicep curls. Just use strict form and somewhat slower tempo. I like to hold the dumbbell to the top of my thumb. Going to have to try relaxing my wrists next time.
Note: the short head will be emphasized more on incline curls. Your peak will be determined by your muscle belly length and the length of your tendons. Good peak is usually long tendon short muscle. IE: Arnold