I see you had some pictures of the AM Northern and were talking about the smoke unit. Take a look at this Youtube video I did of a AM Northern that I reworked with a fan driven smoke unit and a 4 chuff synchronized with the puff. I even sent this to American Models and spoke to Ron about it at the S Fest.
Jonathan, yes you correct. I have been using Electricc RR components for the last 12 + years installing TMCC in engines and specialize in "S" gauge and Jon Z has done a great job. The sound board he has is now one board and there is even a small cruise control board that he came up with that has been working out great! I have not come across any engine that is not conducive to installing TMCC in "S" gauge.