I use doubles all the time, but never two exact doubles underneath the lead. YMMV. I don't know anything about Cubase, but in Pro Tools it does not make a difference because you can still write all the automation in the individual tracks, and you still have a fader for every track. When you need to print vocal up +.5, -.5, +1, -1, etc. mixes having an Aux Track fader there at mixdown makes the adjustments a lot faster than adjusting the automation on every track. When making a stem the individual tracks still have to be routed to another Audio channel to be printed, so what difference does it make if there is an 'Aux Track' in between or not? Pro Tools labels it's "sends & returns" in the I/O setup as busses. There is no need to get angry. 'Sends' are used to route the signal to the buss, and the 'Output Assignment' of the 'Aux Track' is used to "Return" the signal wherever you want it, but nowhere in Pro Tools is there anything labeled "Return." Every console is different, and so is every DAW. Knowing how an SSL4000 G+ works isn't going to help you mix inside a DAW, and vice versa.