There are many answers to this question. There is no ONE right way to punch, but there are many techniques that can help you learn to deliver the maximum effectiveness with the most safety to you.
Here are a few suggestions, but no online answers to this question will afford you a safe way to learn. I recommend an in-person teacher/coach/trainer.
1. Isshin Ryu teaches a way to lock the wrist tightly, using the radius of the arm in a straight line to the forefinger knuckle by beginning with a sun-fist posture (fist with bridge up, like a thumbs-up with the thumb tucked safely) and cocking the hand downward slightly, creating a straight line from tip of elbow to first knuckle and striking with the top two knuckles or top knuckle only. This is a very effective way to strike straight forward.
2. Wing Chun features several basic types of strikes and blocks (and they are not seperate - each block is also a strike). Most of the time the fist is simply tightly rolled or the hand is straight (sword-hand), or the hand hooks at the wrist similar to crane fist in order to strike with the back of the wrist or hook downward an opponent's arm. All of the techniques taught are effective, and practice on wooden dummies is crucial, since it creates a vibrational frequency which builds the bones stronger and thicker as you work it.
3. Ba Gua teaches eight hands and they are all worth investigation. Depending on the exact situation, various strikes may be most appropriate.
As far as generating power in the punch, please consider that there is an ancient teaching from Kung Fu that is stronger than the use of hip movement and generating power from the waist. The best power for strikes or any other martial movement is generated all the way from the ground, and is separate from the body itself. The strike should be as if the opponent has hit the ground itself, steel or concrete. There is no more effective technique for power generated, but it takes in-person training to understand how to do this. Suffice it to say that the "power from the waist" philosophy is more popularly known but not as strong as the "power from the ground" methods.
Instead of choosing one way you think is right, try not to limit yourself to one. Think, instead, of learning to use each method effectively. Also, simply studying American Boxing and working with bags can instill the proper striking skill, while teaching speed, power, and rhythm. Technique (as studied in various martial arts systems) along with the benefits of boxing training may be the answer to the best "punch" techniques.
Think of training on a Maki-Wara board also, as you progress. It's from Karate training and has value as much as breaking techniques do. From Kung Fu you may select to try Iron Palm training, using hot beans and/or bean bags or sand bags in your conditioning. A formal study is necessary to gain the proper strength and internal ability. I recommend, once again, a proper teacher, so that you may avoid injury and get the best value for your training time.