Is there a preference over Type A or Type B for specific installations? Documentation indicates that Type A is generally suitable for residential applications, when is Type B better? Is there any recomendation based on the length of the cable?

Shouldn't be any difference just whichever you choose keep it the same throughout your network. If you mix them up you will be in for trouble. I can't remember exactly but for best connecton and least loss i'd keep the runs under 300 feet.

Are you talking about the color coding on the jacks? If so, there is no benefit of one over the other. The difference is what you are using it for. The A color coding is for digitial phone lines, while B is for data (ie. Ethernet). These are industry standards you should stick too in case you ever have an outside person doing work on your network.

why would anyone use cat5 cabling for a phone line?

568B is an old ATT and standard. TIA/EIA standardized A & ATT walked out of the process (1985) mainly becasue ATT had millions of B wired jacks in the field. ATT carried a big stick so the committee allowed with A or B wiring. The difference is pair 2 and 3 reversed. (orange,Green). It doesn't matter which you use as long as the jack and the patch panel are the same. A wired jacks are residential because that puts pair 2 of a standard phone jack set to pick up line two of a two line phone. If a resi jack is B wired then the phone company will need to wire line 2 on the green pair which no will would figure out. Blue/bluewhite is always line one and in the center postion of an 8wire or 4 wire jack. This would be the old green/red of Plain old telephone wire (POTS) Most people don't use two line phones anymore. (The kind with the manual button ) I'm not talking about KSU phone systems. Your city usually wires either A or B depending how the phone company did it before the break up in 86. This is probably more info than you need so just use one or the other. By the way it a good idea to wire phones with cat 5E because the price isn't that much differenct and you will be set for voice of IP in the future. Good Luck !

oh by the way. You get 100 meters of Cat5E,Cat6,STP, or multimode fiber in a horizontal run to the desktop. 90 meters of solid cable called the basic link and an additional 10meters of stranded cable for patch cables at the work station and in the closet.( jack to Nic, and patch panel to switch) If you do the a math a meter has 3.23 feet so keep your horizonatl to 295' and total patch cables around 30'. The stranded wire slows the data so its used for its flexibility around desks,chairs etcc...