Owning a RED and working with it for a while, I thought I'd chime in.
First, the RED records at 48k/24bit, no other settings exist.
If you send line level, and set the RED to line input (you have to verify 48v is disabled) you basically bypass all the audio pre-amps and board components and record the signal direct to the file. If you set the RED to Mic input, you are now enabling all the audio pre-amps and related components off the audio boards to pass the signal through before it gets to the file. Unless it's a Mic direct into the camera, I set up or request line level inputs as it's always been better quality than Mic level.
Here's where I get my menu guides to be able to find everything (about half way down the page): http://www.octamas.com/red-one.php
To set a RED up for line level input on 30.5 (or many previous builds) the order of the steps is important:
[list type=decimal]
[*]Press System button
[*]stick 2 to the left and press stick down to select Sound menu
[*]stick 2 right and press down on 48V MIC
[*]press the stick to uncheck all these, move stick left/right to go to the next one
[*]Press Exit
[*]Press System button
[*]stick 2 to the left and press down to select Sound
[*]press down stick on REC Enable
[*]pick which channels your using and twist to select Line
[*]uncheck any channels your not using
[*]Press Exit
[*]press Video button
[*]stick 2 to the right and press down to select Audio
[*]Then click to enable your channels and set these to Line and 0dB (10dB if a tape input) this is unity for the RED
[*]send -20dB tone from your mixer - Important must be -20dB!
[*]adjust mixer output so the green bar from the tone touches the vertical white bar on the channel meter on the RED LCD (or a bit less just in case)
[*]Explain to the camera op "don't touch anything related to "Sound" or "Audio", test, re-test.
If you don't turn off the 48v, your stuck in Mic input mode but it might look like your at line levels... Once your more familiar with the red menu system, you can skip the "press exit" and just up-stick to change menus. I still press exit just to make sure things stick.
If something isn't working right, repeat these steps to find out what the camera op changed
Joel