Thank you @gunrunnerjohn for your help and confirming the lighting. The lighting and the couplers is pretty cool.
If I can follow up with one more question. Do I need to build a new TR for any combination of units I run to make sure the lights and couplers work correctly? So perhaps TR9 as the standard ABA, but TR8 when it’s ABBA, and (say) TR 7 when it’s AB?
The above seems like that’s what I’d need to do, but would like to confirm.