At the small scale, how well mixed is the various types of hydrogen in the interstellar medium?

There seems to be molecular gas in clouds abutting ionised HII regions, high velocity clouds travelling through Coronal and cold/warm atomic gas.

Is the plasma in the ISM moving enough to be constrained by its own magnetic fields into filaments?

Hydrogen gas is diamagnetic so repelled by magnetic fields. Does this mean the ISM is like a plasma globe full of cold gas with hot glowing filaments that don't mix?