If I understand your post the QU16 will be used in your church and not the QU Pac.
For the QU16 to do what you want to do you will need to use the aux mix outputs.
First set mixes 9/10, 7/8 and 5/6 all to post fade and post processing, then select each of those mixes and and set all the channel send levels to unity (about 75%), then hit the SEL button for that mix master fader in the processing menu you can set the delay time as
well as EQ and compression/limiting. You may want to roll off some of the low end on the loop feed.
Using post fade aux sends those levels will track what is done on the main mix layer.
If using the QU Pac you have two matrix mix outs as well as sub group outputs…..how ever to get to all of those at the same time you would need to use the stage expansion box.