Also the large Passenger Train by TheArmyGuy doesn't work with this nor the Lego Freight Train add-on, they snap to the tracks but don't turn.
neither have support for this mod, they weren't made with this mod in mind. they snap to the axis their vehicle spawn is on, not the tracks.
in order to "fix" them you will have to remove the snapping code from the trains, and add "isTrain = 1;" to the train's datablock definition.
true, there should be a way to couple trains and make complete rolling stocks. it’s also pretty difficult to make turns since it takes two tracks to take one single turn
i was working on multi-car trains but didn't find a good way to handle it, unfortunately i dont have the time nor interest to try the problem again anytime soon. maybe in the future.
there haven't been any multi-car trains that existed along with a dynamic train track system afaik. the best you could do iirc was run two trains right behind each other with chrisbot's train mod, but it wasn't reliable and derailing happens a lot more with his mod.