Hi Eric,
You might be interested into this article:
Desktop-Processing-DJI-Phantom-4-RTK-datasets-with-Pix4D
Then regarding flight plan, there is no option to plan a flight a several altitude within one single flight.
You would need to do several flight at different altitude and then process all images together.
The camera angle cannot be set up neither. But if you choose a circular mission, the camera will look at the center. However you can define the capture angle which is defined as the angle that separates consecutive images. (Smaller angle, higher overlap).
Images should be taken with high overlap: 90% of overlap between images taken at the same height and 60% of overlap between images taken at different heights.
You might be interested into this article as well:
Step 1. Before Starting a Project > 1. Designing the Image Acquisition Plan > a. Selecting the Image Acquisition Plan Type
Hope this will help you with your project.
Best,