Sort:  

More specifically, witnesses are just made up unique names? No need to register them anywhere?

Can you generate a single WIF Private Key, and then make up 100 witnesses and 100 miners with that same key?

That is 100% correct to my knownledge. I would highly advice you name your witnesses
furion
furion2
furion3
furion4
I recommend this so that the majority of your mined steem power goes to your main account.

Does the majority of mined SP go to first account due to alphabetic ordering?