I was looking a putting a double barrel stove in the garage but it took up too much room.

If you are trying to bypass the roof, use joints with 45˚ or less angles. It will make it easier to clean the pipes. You can add a topper on the pipe to keep critters out and catch some ashes.

Just reread post #28. If the pipe will exit out the CB wall, use 90˚ joints. I don't know what code would be for single wall pipe through an exterior wall. I don't see a problem but I'm not expert.

How close are you putting the stove to the brick (house) walls? I think the min is 16" but those stoves can put out some heat. You might look at adding an extra heat layer to the brick. Maybe something like aluminum sheet metal with 1" square tubing for mounting.