Napoleon NZ26 Chimney questions

Hi All,
I have a few questions about the chimney for my new Napoleon NZ26 ZC fireplace.
I would like to run double or triple walled stainless steel from the top of the fireplace. It will go up approximately 3 feet and then go out through the exterior wall and then continue up the side of the exterior brick wall.
My question is whether there is a wall thimble that allows the pipe to penetrate through the wall at a 30 degree or 45 degree angle. It seems that this would be more efficient (better draft and cleaning) than passing through at a perfectly horizontal angle and putting a tee there.
Also, the top of the fireplace will be enclosed to the ceiling. Should I be worried about excessive heat build up inside the enclosure.
Finally, why is an anchor plate needed at the top of the fireplace box? Can I just fit an adapter inside the fire box outlet and run the stainless from there?
Thanks for any help

Thanks Begreen. I guess I'm not clear on what offset means. I am assuming that it means that there cannot be a bend that is sharper than 30 degrees, or does it have something to do with how far away from the fireplace the stack can be? If my assumption is correct, then I would like to know the proper process for running my stack through an 8" thick exterior wall (4" stud wall, and 4" red brick) at a 30 degree angle.

Thanks again Begreen. I really am set on running it through the wall. If I go straight up, I have two floors plus an attic to go through. Most importantly, my roof is slate. It seems more economical and safer to run the pipe through the wall to the outside. I did not think about the water issues, but I should be able to fabricate some type of shield to prevent water from getting in.
I did find a 30 degree wall thimble on line, but it doesn't provide any specs. I will have to call to see if it can be used on an 8" thick wall.