I'm using canon 5D MKII, i can adjust the recording level from 0dB to -40dB on left and right channels so i am assuming stereo recording.
the only other adjustments are setting sound recording to Auto, Manual or to Disable.

By head room, i assume you mean knocking back the dB further towards the -40dB end of the range? (Sorry for the dumb, this is all new to me, i usually just set everything to 11!)