You should be able to control the amount of level sent by any channel to the Aux Out channel that is feeding the Aeros without impacting the main mix. I don’t think a mixer can truly say that it has Aux channels without the ability the control the signal to them. The BB channel will just have none of itself being sent to the Aux Out that is feeding the Aeros.
BTW, this is why I said in my initial post that you get more flexibility with mixing levels and monitoring using a mixer this way. If you already have a mixer anyway, it’s a valuable lesson to learn how to use its features. It’ll up your game. You can make quick mixing decisions and adjustment to everything in your rig without effecting the other things, which is nice. It comes at the cost of being slightly more abstract and may take a minute to wrap your head around; so worth it though.
To start, just read up on how to use Aux channels and their typical use cases, which is normally presented as how to make several independent mixes for stage monitoring, and I think it’ll become clear. If you are familiar with playing on stage and asking the sound engineer to give a little more guitar to your mix, what he is adjusting is the level of the guitar being sent to the Aux Out feeding only your monitor.
Now, if your Aux channels have returns (they usually do), this is where the Aeros Outs would go, but you don’t have to use them. To explain, Aux channels get used for several things. Stage monitoring is just one use case … the signal goes out, but it doesn’t come back. Another use case is sending multiple signals to fx units such as reverb, and then having the fx signal return to the mixer. That’s the purpose of Aux Returns, but you can also just feed the output of the Aeros right back into 2 new mixer channels instead of the Aux Returns. These 2 new channels that Aeros goes into will also NOT send their signal to the Aux Out feeding the Aeros, or it would create a feedback loop. Anyway, that’s how I like to work … using Aux Returns can be limiting and I find they are only necessary if I’ve run out of mixer channels.