1. These are simply "fluff" armies that were used in some of the stories that are told in the supplement. It allows you to potentially field it as it was in the story but it doesn't get any rules or benefits.
2. If you're hitting a unit like terminators or wraiths then hit them with large numbers of boyz and keep your big boss guys out of that fight if at all possible. I wouldn't throw a boss into that fight even if he had an invulnerable save.
3. The mega force field is worth its points. The problem is you must take a mek from either the thrakka supplement detachment OR from one of the formations in the thrakka supplement . You cannot take that force field if you use CaD or the main Ork codex detachment. I personally do not think the supa cybork is worth its points. You usually take painboyz anyway so the
FnP it grants is redundant and I never really get use out of the eternal warrior because I try to keep my boss out of big challenges where the
EW would be useful. I honestly havent heard too much hype about supa cybork so I assume no one really likes it. Maybe in the greentide to keep him and his infinite Waaagh! going but that's the only place I could see it.
4. Yes. This is a common ork tactic. You can hide the mek from most things that can cause him death and like you said, it gives a save to every wagon.
I dont always run warbikers, they're not required to win but if I do run them I take Da Rippa as my warboss (his rules are free on the forgeworld page, just go to downloads, then dreadmob army list and he is one the last page) because he makes them troops and in CaD that give them Objective secured and I take two full units of warbikers with a pain boy and a nob in each. That gives me 30 total warbikers and that doesnt count my two warbosses (one being Rippa) or my two pain boyz on bikes. I have a third unit but I can never fit it in.
Automatically Appended Next Post: This thread is really good and I suggest to to alot of people that ask ork questions:
http://www.dakkadakka.com/dakkaforum/posts/list/608882.page
This one has also been enlightening as it is new and gives more tactical advice on how to use boyz. They really are a powerful tool in this edition.
http://www.dakkadakka.com/dakkaforum/posts/list/636159.page