I like all three of those, although in my opinion they should all be good guys (without the inhumane culling of the lower-level herds stuff.) I'm pretty fond of the whole post-human genre, but most sci-fi still revolves around anyone who casts off human flesh as being inheriently evil.
(as an aside I've been trying to figure out a way to write a hidden AI/sentient bot cabal for GH1, ala the group of rogue AI's in Ghostrider 2099.)
So, yeah, the thing is, I like the idea of them as being fairly much human, because the more human they are, the more the meaningless distinction between them and the lower-level citizens stands out. However, with that said, they have to have a way of maintaining their power, both from internal threats, and external threats. Internally they can just use brutal guards, but the more low-tech the brutality they use internally, the more likely some external source is going to say, "Okay, yeah...no, that's enough of that."
The easiest to maintain advantage as a technocrat is monopoly supply of a product everyone wants. A certain weapon, an immortality drug, whatever. The next best is simple technological superiority, however even the best armed can be overwhelmed by a large enough force of Buru Buru. The final option is outright doomsday Mutually Assured Destruction.
I've no doubt that every now and again L5 law gets fed up with the pirates and does a full sweep of the lower-levels, tossing half the population out the airlock, and is being pretty merciful at that. But there has to be some mechanism in place protecting the upper-levels from recieving the same treatment, otherwise they wouldn't have the sort of 'entrenched' system neccesary to keep the low-level citizens low.