New Lionel consolidation

The motor won’t be you’re limiting factor.  The weight of the engine, how good the traction tires are and the weight of you’re twenty cars.  I would think 20 cars a little much for this smaller size engine.

I have a MTH Pennsy Consolidation and it can pull 15-20 with no effort. This locomotive is from years ago also

I would be surprised if the '23 volume 2 Consolidations are any different "under the hood" from the Pennsy-style consolidations in the 2018 big book.  The motor in those was a medium-duty Mabuchi RS-385PH, and I believe the gear ratio was 16.5:1, back-drivable.

I don't think that you'll hurt the loco pulling 20 free-rolling plastic cars on flat track and broad curves.  By free-rolling, I'm excluding die-cast metal cars, and passenger cars with the added drag of pick-up rollers and wipers.  Any more than 20 freight cars, and I think you would be working the loco pretty hard.  My $.02.

If you're pulling modern cars with needle-point axles, 20 cars on level track is child's play.  The plot thickens if you're running on grades, or pulling older post-war cars that have more rolling resistance.

You're worried about the Consolidation pulling them?  How about a BEEP with no traction tires and five heavyweight 18" passenger cars?  Like I said, level track is easy.

After watching any Mr Muffins train running videos I never worry anymore about putting too many cars behind any new engine. I know he MU’s some trains but also runs single engine.