Well I did mention it in my first post too, but to answer yes, the right torque is the key to good head sealing. If you apply too little, the head won't seal cold and the bolts will eventually work loose and then it won't seal at all. If you apply too much, you overstretch the bolts and ruin them or you ruin the head or block. Our hobby isn't nearly as precise and proper as a car engine shop would be, but the goal is to get the screws tight enough to seal but still have some stretch left for when the engine heats up. Using the bolts supplied with the engine is also important, because they were chosen for their stretching characteristics.
When you are tightening screws, you can feel the stretch limits if the threads are clean. As you go in, you feel the bolt seat, and then a steady rise in torque needed to turn it more. If you keep going, you will then come to a point where the torque needed to go in more rises substantially. That's the bolt's limit of stretch. Not long thereafter, the bolt will break. All this assumes that the threads don't fail first, but in our engines they will. For our purposes, tightening down until the screw seats and then just a little more (1/3 to 1/2 turn) will give enough stretch to keep the head sealed cold and keep the screw from vibrating, but will still allow plenty of stretch when hot to keep the bolt from fatiguing. You need to retorque after a few thermal cycles because the stretching when hot puts a permanent set in the bolt. Guitar players see this in the initial string stretch they have to do when replacing a set. Once that permanent set has been made, the bolt will stabilize dimentionally and will keep its torque setting. The better quality bolt you use the faster this happens and the longer it lasts. Eventually, the metal will fatigue and start taking a permanent set again, but our engines will be long gone before that happens as long as we are using the stock bolts.