All the ERR sound boards will work in conventional mode without the command board.
If you want chuff, you will have to install a chuff switch, which will probably come with the sound board.
You put a magnet on the inside of a tender wheel and point a reed switch at it. That yields roughly 2 chuffs per revolution. Adding a second magnet will give approximately 4 chuffs per revolution.
The whole installation is easier than the installation instructions make it out to be.