See also
Signal flow/gain staging diagram for Octatrack MKII
(Unity settings)
Imho most important is input signal, mixer gain.
Edit : leaving it at 0 and adjust your input signal? I’d do that but I’m not sure if it’s the best. If anyone can shime in about that…
Red is a warning (-12db imho), it doesn’t mean clipping. It can be full red without clipping with a sine wave for instance.