I would use a B-vent wherever you can due to the fact that it is a double wall pipe that needs 1 inch clearance. Single wall clearances are much larger (6 inches I believe).
They even make B-Vent adjustable 90's.
A wall thimble is used for horizontal penetrations in walls. It gives you the 1 inch clearance by design.
A fire break is used for ceilings. The tabs forming a square around the circular hole give you 1 inch clearance as well. If you were going through the ceiling, I would recommend that you add metal duckwork from any hardware store to the tabs..... the ductwork should rise well above any blown in insulation. It is FAR easier to do this now at ground level, than to add it in later in the attic.
This enclosure will give you the one inch clearance around the pipe for any insulation to rest against. If you feel super ambitious, cap the top where the pipe exits your protective sleeve in case you have a careless blown in insulator who fills the space or other debris could get in.
R
