Question about RL agents controlling other RL agents

Hi, I'm a beginner in the field of reinforcement learning, currently interested in physics-based motion control.

As I was looking at various well-known environments such as the Robot Arm, a question occurred to me about how one would attempt to perform well in a physics based environment involving controlling such models to achieve complex tasks that are more abstract than simply reaching a certain destination. Particularly, the question occured from this paper, with the image of the problem scenario shown below.

https://preview.redd.it/wrvz16y7flee1.png?width=612&format=png&auto=webp&s=5c24cb87a696247929aff41e8775833c617b9218

For example, say I were to create a physically simulated environment where the Robot Arm aims to perform well in an online 3D bin packing problem scenario, where the robot arm grabs boxes of various sizes from a conveyor belt and places them onto a designated spot, trying to fit as much of them as possible in a constrained space.(I guess I could model the reward to be related to the volume of the placed boxes' convex hull?)

I would imagine that having a multi layered approach of different agents may work adequately, one for solving the 3D-BPP problem, and one for controlling the individual motors of the robot arm to move a box to a certain spot, so that the 3D-BPP solver's outputs may serve as an input for the robot arm controller agent. However, I can't imagine that these two agents would be completely decoupled, since certain commands of the 3D-BPP solver may be physically unviable for the robot arm's movement without disrupting the previously-placed boxes.

In scenarios like this, I'm wondering what is the usual approach:

  1. Use a single agent to be able to control these seemingly distinct tasks(solving 3d-bpp, and controlling the robot arm) all by itself?
  2. Actually use two agents and introduce some complexity into the training sequence so that the solver can take the robot arm controller's movement into account?

In case this is a trivial question, any link to beginner-friendly literature that I could read up on would be greatly appreaciated!