Taiwan is not (yet) on the list. So far, you can do a customs-free international-to-domestic transfer on AC & WS flights arriving from the US, Europe and Australia. There have been some trials with a few Asian airports, and the list of approved origin cities will only increase: Creating a Connecting Hub YVR

At present, the transfer takes place by bus; a side door in the arrivals hall leads passengers to a bus which drives them (3 minutes) to Gate 29 in the domestic C pier. Planning and initial construction is taking place to enable that transfer to take place inside the terminal building...anticipate at least couple years down the road, so to speak.