Starting development for new airframe

Hello, Developers, I need really efficient suggestions from you all.

I have started development for new airframe that is somehow related to quadrotors but have many some structural changes. This means, I need to add my airframe for better results.

Upon researching Px4 tutorials, I have some questions.

Is there any tutorial that will give A-Z details of creating new airframe. What are the important components of firmware, we need to change and tune.

Also, I am developing ROS package for my robot. Are their tutorials that how do we add and integrate the urdfs of our robot with PX4 App.