I’ve read all of the Del Ray collections, so that’s most all of the original REH Conan stuff but not the pastiche stuffak that was added on.
In terms of technology…REH was wildly inconsistent about this. Stygia is a pastiche on Classical Egypt, the Vanir and the Aesir are Vikings, Aquilonia is a mix of the Roman Empire and the Carolingian Empire (but some of their armor is clearly late Medieval), Argos and Corinthia are Classical Greeks, Zingarans are more Renaissance Spaniards, the Turan Empire is an Orientalist pastiche of Crusades-era Arabian/Persian/Turkish empires, the Hyrkanians are Mongols, the Pictish are a really racist take on Native Americans of the southwest, Hyperboreans might as well be The Greys, everything directly south of Stygia is a pretty racist take on precolonial Africa, the Barrachan Islands are the Caribbean islands during the Golden Age of Piracy, and so on…