Went MIA as was tied up with work.
But ya, essentially there's no standard. All manufacturers do it their own way. Generally Mic outs are weak, non-amplified. Audio outs are a cleaner, stronger signal compared. So long the connectors (ie. XLR-XLR, 3.5-3.5, 6.35-6.35, optical-optical, RCA-RCA etc) are compatible, it should work, just loud/soft.
For 3.5mm take note that there are TS, TRS and TRRS connectors. for the 6.35mm, TS and TRS.
Generally wireless mic receivers need an amp. Without 1, connecting the mic out to a powered speaker is unlikely going to give u the desired results, and instead u will end up with weak or no sound from mic at all. Hope this helps u with ur shopping considerations