If your wanting to use two QU mixers both connected to the AB168 stage boxes then no you can not do that, an SQ and a QU would work.
With QU mixers if you want to use two independent mixers you need to use a hard wired
splitter to feed them.
Using a remote iPad connected to the QU32 you can control a mix within the QU32 independent of the main house being done on the surface of the mixer.
Doing that you can control mix send levels, mix output levels, output processing and set up a dedicated FX mix but any channel processing changes would affect the main mix as well.
If you have extra/open channels on your QU32 you could then split the input channel either in the patching routing or with Y cables for any local inputs. Splitting the
input channels into two channels would let you have full channel processing on the live stream mix, if you do that make sure you un-assign the second split channels from the main mix.
If you do not have many open channels maybe just split that channels that need more attention on the live stream mix.
The iPad could still be used with the channel split option.
If your trying to do something completely different let us know.