My first introduction to live steam locomotives was a member in our railroad club had a Accucraft Ruby locomotive. It is G scale (45 mm track) and a very simple design.
He had a radio control (RC) receiver and servos to control direction and speed of the locomotive.
Then my wife bought me an AristoCraft 040 live steamer that had a built in RC and sound. It is much better than my Ruby as my Ruby does not yet have RC installed.