Like any other tool, understanding the assumptions and conditions of a solver is important to get correct results. Nost likely your first application of the tool will not result in incorrect results, however after gaining experience in using tool and understanding on which cases it works and does not work you will then be able to build trust and get correct results

Not yet, but this will be possible in a future update 

For electrostatics, you can import meshes as an STL file, it is recommended that you clean-up the mesh using the Limited Dissolve operator and then using the Remesh modifier.

For magnetostatics, you can import lines as a DXF file and convert to a curve

That depends on the complexity and mesh size of your scene. In most cases you certainly do not need the latest and greatest CPUs and GPU. However it is recommended to have a machine with 16GB of RAM or more