first welcome to audiofourms.com
as for mixing boards...
stereo is simply 2 channels, a right and a left.
and aux send is a channel too
so is a sub bus.
so is a "mix-b"
there is nothing special about any of the outputs of any mixer.
all of the outputs are equal in quality and signal. (sans the unbalanced RCA "tape outputs" found on some low end mixers)
different mixing consoles simply have different routing options.
like a matrix, or an aux send or a sub group or L/R master out.
most mid to high end "consoles have a multiple sub bus groups outs"
like a mackie 16x8 has 16 in 8 sub mixes out, a stereo R and L out plus 6 aux sends and a few other options like a mix b, control room out, ect...
for a total of 16+ channels of output.
and that is a lower end mid level mixer.
pretty much anything above that level of mixer will have far more than just two channels of outputs.
regardless, what you are looking for my friend is a piece of equipment called an "audio patch Bay"
this will let you plug in all of your processors, compressors, limiters, echo chambers, Parametrics, graphics, what ever.
then all you have to do to use a piece of equipment is connect a patch cable to the apropreate equipment connection to make the patch. you can also link multiple pieces of equipment together in any combination using parallel or serial connections.
check this out here:
Enjoy the Silence.....