The new EnergyPlus Python API is really a different beast that the other APIs you listed. The key for each API is to understand what it does and when it is used.
OpenStudio, eppy, jEPlus, and Modelkit/Params are all APIs to modify/generate simulation input files, manage simulation execution, and read/process simulation output files. There are differences in functionality, programming language, and other details but each of these APIs has functionality in these areas.
The EnergyPlus Python API is really almost two APIs. Library mode allows another program to call routines in EnergyPlus directly, previously the only way to access these routines was to write an IDF file and execute a system call to EnergyPlus. Plugin mode allows EnergyPlus to call Python scripts at each timestep during simulation runtime as part of the simulation itself. For instance, your Python script could be used to control some piece of EnergyPlus HVAC equipment during the simulation based on logic in your Python script.
A user could easily use multiple APIs as part of a workflow. For instance, you could use OpenStudio, eppy, jEPlus, or Modelkit/Params to generate a large number of IDFs and call EnergyPlus to simulate them. Then, during the simulations, EnergyPlus could call Plugin API Python Scripts as part of the simulation to control HVAC systems. After the simulation, OpenStudio, eppy, jEPlus, or Modelkit/Params would read the simulation results and format them for the user.
There is a similar post here asking about EnergyPlus APIs in general for more context. There are also good posts here explaining the main goal of the Python API created by the EnergyPlus development team and here with links to EnergyPlus documentation about this feature. A full write-up of differences between each API you mention will likely be pretty lengthy.
Thanks for sharing all these. It helped!