Steven:
Clancy has been on an Alaska vacation for the last couple of weeks. I will try to answer some of your questions, but I am sure that Clancy will respond with more expertise than I.
Clancy's system gives you an encoder for use at the flying handle. That unit sends a signal through insulated flying wires (wires not provided by Clancy). Then Clancy provides a decoder (the receiver that you asked about) with the system to be mounted in the airplane. It also connects to the flying wires and interprets the signal for the servo or electronic speed controller (ESC) if you are flying all electric. Clancy uses a servo for throttle on his fueled airplanes. I use an ESC control for the electric motors in my airplanes. Yes, you will need a battery (4.8 V or so) on the airplane to power the decoder and servos. That is, unless you are using an ESC. In most cases, connecting the decoder to the ESC provides power to the unit. There are some exceptions to this (for example, when the ESC might be optically isolated).
I believe that Clancy is still making a seven channel unit. I bought one from him and have yet to incorporate it. I will, but I also have two of his four channel units that are doing the job for me. For example I am using his four channel unit in a scale Beechcraft C45. It is doing throttle, retracts and flaps with one channel left over.
I hope this helps. By all means, make sure you get in touch with Clancy.
Jim Fruit