The stuff you described there is literally just one AI routine, "sandbox". They just added more ways for actors to interact with objects in the world. Unfortunately, they also gimped schedules a lot. For example, on the 7th of every month, you could find Quill-Weave, an Argonian from Anvil, walking on the road. You could follow her and find that she's going to visit Casta Scribonia, another writer in Chorrol; you can then watch her stay the night at Casta's place and head back to Anvil. If you kill Casta Scribonia, she will not make the trip, as she has no reason to go to Chorrol. She also goes to a formal dinner that Milona Umbranox holds every Sundas and Loredas. Skyrim doesn't have anything like that, AFAIK, and you can find something like that practically every other day in Oblivion.
Prequel is actually really indicative of why I like Oblivion better than Skyrim. Oblivion actually gives you enough of the individuals' schedules and enough dialogue that you can fill out a personality for each one you meet, and Prequel really manages that. Quill-Weave is a fairly major character in that, and the formal dinner with Umbranox is brought up as well as her relationship with Casta Scribonia (which, in fact, isn't actually stated outright in the comic at all, and has to be guessed from minor hints in the comic combined with knowledge of this friggin obscure NPC from a single fighter's guild quest in Anvil).