PS DCC system output to your rails is neither DC or AC voltage. Said meters do not give you an accurate reading. It is DCC. You need a meter that can read DCC.
To be accurate, it is some form of AC or DC (pulsed). No way around it.
A serial data transmission who's signal is based on the frequency of a change in signal is more accurate. It piggy backs the motor power or via. Radio waves.
Correct. The DCC signal is AC. Its not a pretty and stable sine wave that one sees coming out of the wall receptacle, but it is absolutely AC.