pymatgen & ASE
I'm a big fan of simplicity and integration in my python-based and Julia-based workflow.
Therefore I typically directly use the visualisation features from pymatgen, such as pymatgen.vis.structure_vtkpymatgen.vis.structure_vtk, and ASE, for example ase.visualize. Mostly I use them anyway to build up my problem. They have some features for analysing results as well, but those I have not used so far.