I cant answer the rest of your questions, but as for what needs more than 4 channels, scaled RC often needs a lot of channels. you have a channel for steering and throttle, then add diff lockers, reverse gear, high low range, triggering lights and sound, winch, channel mixing for front and rear steer...thats 7 channels already. There might be other accessories you can add which will take up more channels hence why Futaba came out with this radio.