I can't answer either question, but both PS2 and Locosounds have speed control (cruise).
I was going to say I doubt you can find any Locosounds boards, but you could do a search on their website to find the latest engine that was offered with Locosounds and when it was.
I'm presently removing a Locosound system out of a RK 2-8-0 and installing PS2. I also have the a RK RS3 with Locosounds. The only issue I ever had with the RS3 was that on occasion, below 50 degrees in the layout room (garage), the engine wouldn't change direction until it got above 50 degrees. I have since moved my layout inside the house and it has worked fine since.
I really like the sound of the RS3, the 2-8-0 isn't nearly as nice as engines with PS2 sounds, the whistle is very monotone.
Does your PS2 in the RS3 work? Would you consider a trade (both Locosounds guts) for the PS2 guts?