>>2521676the latter.
I don't know how to check real-time physics in blender, but if your model has rigid bodies and joints then it has working physics on it, they will be automatically ported to .pmx
to port things you'll need this:
https://github.com/powroupi/blender_mmd_toolspull on highlighted arrow for more options.
..but I may be wrong, since I never worked with non-pmx models