I've actually been in the same boat trying to replace everything that needs replacing with Delco or Delphi.
I believe you have your acronyms confused. OE is original equipment, anything that came on these off the assembly line. OEM is original equipment manufacturer which AC Delco and Delphi are. And as you've seen, AC Delco has different quality lines. Specialty, Professional, and Advantage.
Specialty parts are few and far between for our vehicles from what I've seen. So far i think I have only seen Specialty rotors which were slotted, painted and coated. Specialty line is above average aftermarket quality. Proffesional is your average aftermarket quality and Advantage would be passable quality stuff. OE stuff will meet GM's quality specs,I think most stuff was designed to go at least 100k before needing some kind of attention. As you said everything is pretty much made in China now so it's all hit and miss across the board, hopefully quality control showed up to work that day.
Anyway, I've ordered everything from Amazon, they're a certified AC Delco retailer, using part numbers off of the AC Delco website using my VIN number.
http://parts-catalog.acdelco.com/catalog/catalog_search.php
Everything I've read or seen states to replace the wheel cylinders when you're replacing brake shoes. Drum brakes should last a good 100-200k miles depending on driving conditions so you're really not doing it often. I'm not trying to go back in there to replace a leaking wheel cylinders down the road so I'm just going ahead and replacing them now. As far as the springs and other hardware, if you live in a state that uses salt and whatnot on the roads I would go and replace everything.
I've decided I'm going to have my OE drums machined before I consider buying new ones. I only have 134k on my Tahoe so they should still have some life in them. If I do buy some new ones I will probably go with the Duralast ones. Looks like the AC Delco Professional casts might have so issues.