Re: Ki and Technique...
Ki and shouting is not the same. However I would certainly say that vocalisation can help to provide focus in generating more power, with timing, and also with disorientating the enemy. I find I use it involuntarily within weapon work since often very urgent and decisive moves with perfect timing are required.
Ki is a very complex subject (covered in many other threads). Simply put it is 'energy' which you can accumulate, and then realse (as jing) through correct posture, coordination and movement. I'm not sure if I believe in the mythology, but it is a good model of how to improve your technique and your health so that you can perform effectively.