I've experimented with several types of grips and "picked the brains" of some of the greatest players like Earl, Johnny, and Buddy about their grips and there philosophy on the subject. Controlling the cue is what's essential and most pros I've talked to change pressure (slightly) according to the shot, although they do have a favorite grip pressure that they try to use most often.
The think I learned from playing other sports is how the wrists move to create accuracy and precision without forfeiting power. I have an easy time working with golfers, tennis players and people that's hammered a lot of nails. I was the son of a carpenter and grew up hammering nails, as was Earl Strickland (he did a lot of roofing/shingles).
The forearms, wrists and fingers can generate a lot of power with ease using a hammer, axe, golf club, pool cue, and/or filipino fighting sticks..
...training with swords, sticks and staffs will really accelerate the learning when it comes to generating effortless power with the hands, wrists, and fingers IN ADDITION to the motion of the arm and forearm.
The "flick of the wrist" provides acceleration and accuracy, like the champion dart throwers demonstrate. The absolute quickest way to improve your game two or possible three levels in a few weeks comes from stance and stroke training. These two areas can be improved in most players I've seen, with the exception of the bone fide Champion players.
When the stance is correct and the motion of the grip is improved it's creates a chain of body reactions that force the player to improve immediately - the game gets that much easier to play when the physical part is handled correctly. 'The Game is the Teacher'