Bob Moulton recently showed his Digitrax Chief system. It can control many locomotives, turnouts, lights, crossing gates, etc. When I was demonstrated it, strange things happened. Later, I found out that it was because the power wasn't turned up all the way. Computers, like people, tend to lose their memory when not operating at full voltage.
Full power is on the track at all times.
Tiny computers, called decoders, inside each loco control the direction, lights, and voltage to the motor. The hand-held cabs send signals to the base unit. First, check out the price for a full system. If not, you don't need it. If so, you don't need it, but there may be reasons you want it anyway.