For a two person interview, you will not need a mixer. Just record one lav mic on the left channel and the other on the right channel. Then during the post, copy your “stereo” audio to a second audio track and select “left channel only” for one track and “right channel only” for the other. Then you can do a mono mix and independently adjust volume for each of you. (Do not, under any circumstance, leave the channels on the left & right extremes. You can pan the channels so the sound moves a bit, but extreme panning will result in a sort of audio/video dissonance.)
Depending on your camcorder, you might be able to independently set record levels for each channel. This is terrific. But I haven’t encountered any real problems in interviews with either manual or automatic settings, depending on the difference in individual volumes. In situations where one speaker is a great deal louder than the other, I get the best results with auto audio. Say when one of the speakers is a young child, especially a shy child. But with two adults, I do prefer to use manual levels to avoid level drops when both are speaking at once.
And by the way, on such a short mic run with a static camera, XLR’s offer no advantage over 1/8″ stereo audio inputs. (As an understanding of the actual difference between balanced & unbalanced audio inputs demonstrates.)
Have fun & I hope you get a great interview.
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