I'd say, save the PH strips for wine-making. Relax 8)
Understanding PH helps you understand the entire process of brewing; but you can make awesome beer for years without understanding the chemistry stuff.
If you're doing extracts... relax, don't worry, it is insignificant. If you like the way the water tastes, use it. Bottled water will never be a problem. Somebody already worried about PH when they made your extract.
If you are talking all grain mash. The mash grains usually levels near the perfect PH of 5.2. Again, if you are using bottled don't worry. With tap water you can always throw in a teaspoon of gypsum. If you've read Palmer, you'll know if any or how much is necessary.
If you are doing a classic beer and are trying to duplicate water from a certain region in the world... understanding the PH will be worth your time. That would be a long answer.