I haven't read any of the links above; however, I'll acquire things (relating to Internet security) on the DNM from time-to-time and I'm very familiar with it, firsthand.
In my opinion, one of the most misunderstood concepts of the Dark Web, is that it's some mysterious place. More than anything else, it's just a way of creating a site that isn't registered by the legitimate domain registrars and therefore the domain cannot be suspended or restricted.
This is obviously done with Tor addresses, rather than conventional domains.
For this reason, the majority of Darkweb (or Deep web as you refer to it) content would be removed if it were using a legitimate domain. In short: it would be considered illegal (or similar).
You also have to look back to the history where this all (sort of) started with Silk Road, a marketplace that used a Tor address for this very purpose, evading law enforcement. This is the reason so many people experienced with the Darkweb, refer to it more appropriately, as the "Darknet" or "Darknet Marketplace" (because so often it's tied to buying/selling).
If you'd like the most definitive overview of the DNM, direct from the most experienced people on the subject, without a lot of excess time/nonsense, just search for the latest copy of the "DNM Bible" (typically uploaded to Reddit as it's periodically updated).
Or, if you don't need something illegal (or you're not into hacking), save yourself the time, there is nothing particularly exciting and there are a great deal of crazy people you generally wouldn't want to associate with ;-)