Hi @slidesinger,
The default Channel Source point for Mixes is Post-EQ/Pre-Compression by default, though the default for the FX Sends is Post-All.
You can change these by selecting a Mix or FX send, then going to the Routing screen and using the ‘Channel Source:’ drop down.
(I think this is what @SteffenR is referring to, apologies if not)
However – it sounds more like you want to insert the reverb before the compression directly within each channel. You can insert FX units into input channels, but as there are a total of 4 FX engines in the Qu-16, you’re going to run out if you want individual reverbs on all those listed.
This is why Mix->Return is the default setup for FX1 and FX2 on the Qu-16, so you can mix any combination of input channels using the FX Mixes, these go to the FX units and come back (affected) on the FX returns.
In this case, what you could do if you’re only using those reverbs on the Mixes of instruments you mention and don’t need to use them in a Mix->Return setup, is to insert the FX units to Mixes 5&6/7&8 instead.
Then, as it sounds like you are looping the mixes back in via analogue I/O to effectively re-purpose the stereo inputs as groups, you can simply apply compression on those stereo input channels.
If you need assistance or more details on this, you can always contact us using https://support.allen-heath.com
Cheers!
Keith.