RT stands for response time, it is effectively a slowing down of the travel. Think fixed wing scale landing gear that you don't want to go whap up, whap down, but slooooowly up, and slooooowly down. Or camera pan that you want to be slow and smooth. There is a thing called a tooltip. Hover the mouse over the input area for one of those inputs and it will tell you all this.
Channel type is all kinds of receiver protocols, like SBus and PPM, those are just some different Rx protocols.
The LED output is for WS2811-2 LED chip. It is a digital signal type that controls the red, green, and blue values. Up to 10 LEDs are driven with a special series signal and all LEDs put out the same color. WIki has colors and blink codes. One might say "GPS warning"; another "ready to arm".