We will be using roll20 to store character sheets and for dice rolls, but otherwise it will be theater of the mind and played here on the forum, in another thread I'll be making sometime around Monday. All of the 40k systems published by FFG are fairly similar in base mechanics, though they have some differences here and there.
And yes, in Dark Heresy you not only play Imperials, it's acolytes in the direct service of an Inquisitor.