Welcome to the forum!
Do not worry about power draw of your locomotives. Most transformers can handle a 2 motor locomotive with no problem.
The larger diesel engines such as the F3's, FM Tainmaster, and the electrics such as the GG1's will have 2 motors. A look at the specs of the locomotive on Lionels' website will tell you if an engine is dual motored.
Power is rated in watts, which is the product of volts x amps.
Larry