Pixhawk 4 & Crossfire Diversity RX in Fixed Wing Twin

New FC user completely out of my league. Just a few of my questions:

  1. think I want to use MavLink connection from Crossfire to Pix 4 but which two wires out of Pix 4 Telem port to channels 8 & 7 on Crossfire RX?
  2. Where do control surface (v-tail) servo signal wires connect to Pix 4 or PMB?
  3. How to set up motors to enable differential thrust?
  4. Where does SmartAudio wire connect?

Is there a tutor I could pay to help me?