If you are looking for information geared toward the home draft system, then the brewer's manual is way more involved than you need to know. They generally have considerations beyond what the average home brewer will deal with, so their manual needs to cover a LOT more detail.
For the home brewer, the basic system is not difficult to understand. Assume the home brewer will use a chest freezer or upright fridge or freezer as a cold storage location (Where the kegs are kept.) Assume they will use a small CO2 to provide beer gas. Assume they will want to use Corny kegs.
The kegs are kept cold in the fridge/freezer. The gas line is run through the wall of the fridge or freezer (or collar if a chest freezer) and it continues inside using a manifold to distribute the gas to the kegs. The faucets are attached to the door of the upright fridge/freezer (usually) while faucets are mounted in the collar of a chest freezer. Liquid lines run from each keg to it's faucet.
Now the important part! The pressure from the CO2 regulator going to each keg must be of a certain range to server a properly carbonated beer. If the beer is subjected to a sudden drop in pressure, that is akin to nucleation points and it forces some of the Co2 out of solution and into a gaseous state. (FOAMING!) Therefore it is important to balance the resistance in the serving line to keep the pressure up while pouring. There are two ways to do this; small diameter serving line, and longer serving line. Both in combination will help to keep the beer from foaming.
Foaming in general is also dependent upon temperature, as CO2 will remain in solution easier when colder.
So these online charts that calculate beer line length are trying to keep the beer from foaming by using the smallest diameter beer line and having it long enough to keep the resistance.
For most people this means 3/16" line and about 10-12 feet of it for the average beer at the average temperature. Note that some styles require more pressure because they are carbed higher, and some less, for the opposite reason. And if you want to mix those two in the same system, then you need to add another regulator head to the gas system so you can have 2 different pressures.
Another way to do it, which I don't recommend except for temporary, is to carb the beer up and then drop the pressure in the headspace and regulator to just a few pounds per square inch. This allows the beer to pour without foam, but it also allows the CO2 in the beer to slowly come out of solution. So it's nice as a one-time deal, but ideally you would want the whole system to be balanced so you don't have to mess with the gas all the time.
I hope this answers the questions you have and wasn't dumbed down too much.
