Most likely, yes to all of those questions. What kind of system are you using, and what kind of decoders do your locos have in them? Also, what kind of locos are they? With Digitrax, I programmed the same speed curve on three locos, along with Acceleration and momentum, so now all three of those will easily consist. (you can put them all on the programming track at once to speed this up) Make sure they are going the same direction when you hook them up too, not necassarily pointing the same way, just moving the same way. Once they are programmed the same and moving the same direction, select the one you want to be a slave and just punch Mode twice and Yes once (on Digitrax). The system might make up for acceleration and momentum, I can’t say for sure since I have it programmed the same anyway. I really don’t think you’ll do much damage to the motors if it’s not EXACTLY the same, as long as the faster of the two can spin it’s wheels, if it doesn’t have enough power or is weighted too heavy to slip it could cause some problems, but either way they should be close to the same or there really is no point in consisting.
Atlas Master SD35 with dual-mode 4-function decoder
Atlas Master H-15/16 with dual mode 4-function decoder
Athearn RS3 with a Lenz Gold-JST decoder
Concor MPC15 switcher with Train Control System 5-function T2 decoder
Proto SW8 switcher with QSI sound decoder