Using a higher chord error will reduce the number of generated triangles and thus the memory used for generating the assets. However with a high chord error you ll lose precision on the resulting meshes. So you might still need to invest in RAM so you can perform tessellation at the expected level.
RAM and CPU will guarantee a smooth experience in your editor when you are working on the scene and rendering your application. However, as you are preparing CAD data (whole car) these requirements are higher and closer to what computer running CAD software are using. On the GPU side: UE4 does not support multi-GPU (SLI), so aim for a high-end single graphic card.
If needed you can split your work on two computers: one for preparation (strong CPU and a lot of RAM) and one for managing your scene and running the experience (a high-end game pc).
Regarding the meshes generated when importing JT: how are the objects grouped in the JT file? Is there a part per body?
More documentation will soon be released regarding use of python.
You have some documentation here https://docs.unrealengine.com/en-us/Studio/Python and examples here https://epicgames.box.com/v/Python-Examples
Have a look at “Unreal Studio Examples\DatasmithImport”. This is valid for 4.19, some refactoring as been done in 4.20.