And whats the consensus of the setting of the output volume knob on the front of the Axe unit ?
I think it depends on what Out 1 is connected to and how it's connected.
I think the output level should be as high as the other side can cleanly handle. That helps reduce the noise floor; Think about what would happen if you reversed that, and sent the minimal signal to the other device and had to turn that up to its maximum setting, you'd raise the noise floor.
I use XLR from my modelers to my FRFR on Out 1 and to FOH on Out 2, and start with the Out knobs at 50% after I've established I have sound through the system. My FRFR are at 50% so I raise that feed to a comfortably loud volume, then make minor adjustments once the band is playing. My FOH feed is set while talking to the FOH engineer and he's monitoring the feed on his tablet, and I let him tell me what he wants; That's usually about 55-60%.
Set your outputs to 0 initially though because bad things can happen if they're at normal volume when you're connecting and powering things up.
And, in every case, it's extremely important to have your scenes and presets leveled.
BAD things can happen if you don't.
PS - Section 4 in all the manuals talks about connecting to different types of devices.
Connections and levels in the Wiki is good reading too.