Total posts : 45366
I believe the aux send is either bal or unbal. Not really an impedance issue in this case, just one of distance and vulnerability to external interference. As long as you keep the patch lines short (preferably 6′ or less) TS cables should be OK.
E.g. on our older Mackie church mixer, I send unbal (TS) from effects (aux 6) to the effects processor, and return it also unbal. The lines are short, right in the console cabinet, and are heavy commercial TS shielded cables. No detectable noise.