I recently acquired an older Williams "Gold Edition" steam locomotive with QSI sound.  Can this QSI board do anything else?  Can it be remotely controlled rather than just do its own thing according to what the engine is doing?  (chuff-chuff-chuff, somewhat coordinated to engine speed, and occasionally a bell when starting up.)  If so, where do I get a controller?  How does the "constant-voltage" headlight work with the track voltage being variable?  (The headlight does not maintain constant brightness.)

I would like to run the track at constant voltage and have a remote control that varies the motor voltage, which is what I think a DCC unit does to control the engine speed among other things for HO gage.  Surely the engine must have a whistle, but I have no idea how that might be controlled.  The whistle control on my standard old KW transformer does nothing for this engine.  I believe the old Lionel whistle controller super-imposed a DC voltage on the track, which the whistle motor picked up and ran the blower in the tender which made a whistle sound with an actual whistle.  Very old school and complicated.  Modern electronics must have made an electronic whistle possible.

Is it possible to upgrade to a DCC control system?  It seems like that should not be very difficult, but I can not find anywhere DCC being discussed or advertised for O gage trains.

What do y'all do to run multiple trains on your tracks without them all going at the variable track-voltage speed and banging into each other?