Programmable Radios can be either PCM or PPM

You can use a Y cable to hook up 2 servos to one channel or you can use a programmable radio and use 2 channels and a mix

Modern FM radios use PPM or PCM as the signal encoding metthod. PCM has the ability to pre-program falisafe servo settings in the event of signal loss or interference (i.e. throtle to idle, elevevator to neutral)