Billk, Woodie has given a most thorough answer and everything he says is correct. I use DCC and have built several railroads in the past with cab control. Cab control wiring isn't all that complicated, there's just a lot of it. FYI, I use Digitrax, and the booster is 5 amp. I have run six locomotives with lighted passenger cars with no problem. The current requirement for a given loco is determined by the loco itself, the decoder only has to be able to handle it. I have only installed decoders in relatively efficient locos, ones that draw .3 to .5 amps. The decoders are rated at 1 amp, so no problem. You are supposed to check current draw of each loco by measuring current while preventing the motor from turning (stalled). I have not done this. That .5 amp could go over 1 amp stalled. In all my years in the hobby, I have never seen a loco stall. Spin its wheels, oh yeah. My advise DCC or not, never weight a loco to the point where it won't spin its wheels.
I run 14 gauge wire, black and white(north and south rails, respectively)under by roadbed, and use 22 gauge drops from the rail to the bus. If you are using turnouts which are non power routing, you can just put drops as required for maintaining reliability, there is another thread on this forum dealing with this. However, if your turnouts are power routing, you need to gap and feed much like conventional cab control. There are auto reversing units available too, you can operate thru reverse loops without flipping any toggles.
My advise would be to check into DCC and if you are going to use it, don't bother wiring for cab control. You still may want to have a couple blocks for troubleshooting reasons, or, as Woodie said, to add boosters later. This can, of course, be added later, by cutting gaps in the rails, and cutting the bus wire also. My reference to troubleshooting means this: If there is a short, the whole railroad goes down. Where is the short? Sometimes it can be hard to find. If you have several blocks, you can turn them off one by one to isolate the problem. My shorts are usually a microswitch controlling frog polarity didn't throw, needs adjustment, or I left a tool across a rail somewhere.
You may want to check
www.digitrax.com They have a lot of info on their site, as well as links to other informative sites.
Good luck!