Best way to implement drone that uses UART connected speed modules

I’m using a Pixhawk 4 mini card.

I need to set up a drone that uses UART controlled speed modules (each module is an integrated ESC and motor, + position sensor). I have all the C libraries needed to connect and communicate to these modules and I can compile them within the PX4 firmware with no problem.

To control the modules, I am going to create a thread that gets the desired control (throttle, pitch, yaw, etc…), calculate the necessary speed for each module and send the commands via UART.

I’m new to PX4, so I’m not sure about the best way to implement this. So here are my questions:

  1. Airframe - I managed to create a new airframe file and I can set it up on QGroundControl.
  2. Mixer - Since each module needs to receive digital data from the UART connection, I imagine the mixer is useless and I shouldn’t use it (meaning that I should just set up a mixer with no components)?
  3. uORB topic - I imagine that I can subscribe to the desired control topic to get the desired commands. I’m not sure how to do it in a way that can use both the manual radio control and a future automatic flight mode. Is there some kind of “control” topic I can subscribe to that will send me the desired yaw, pitch etc in both modes?
  4. Main control thread - Once everything works, how can I set card up in a way that it launches this main thread once it’s activated?

I’m sorry if this isn’t the best place to ask these questions, but I’m very new to the PX4 and I couldn’t find the answer to my specific set up.