I and Eiger Nathan have both with our own homes done extensive renovations, essentially gutting the places where we live with our families. This is actually a great topic rich in a lot of legal and non-legal issues.
Some quick notes:
1. Architect's fee: by %, and that is often negotiable and may depend on how and whether you know them.
2. What is the architect supposed to do: Some guys are really more "idea" people, while others are more like general contractors. It's good to find someone who has nice, beautiful plans and yet knows how to work them within the limitations of your home. I found it important to have a guy who understood how homes really are used and need to work, and so we have electrical outlets in the right places and rooms and storage spaces are appropriately sized.
3. Prices on the architect's side of things: Architects will normally get some discounts, but keep in mind that many suppliers may have some form of kickback setups by which the supplier essentially "thanks" their source of regular business. We had an architect who agreed upfront that if we found a better price somewhere he'd try to work with his supplier to match it or else he'd be willing to work with the supplier we found. My wife did enormous amounts of private research on air-conditioning systems, windows, tiles, kitchen cabinets, doors, the glass shower area walls and doors, etc. and was able to cut down a huge amount of our costs for our renovation. Most indicated that there were some discounts from when they sold to the architect.
4. Remodeling price per ping depends greatly on the quality of the work to be done, the materials, and whether you are willing to hear every snore or other noise from other family members in bedrooms nearby. I've heard some people renovate for approx TWD 30,000 per ping, but that often means simply sprucing up an existing layout, having kitchen cabinets of the very local type (and somewhat lower height) made of sheet metal with the plastic doors, and perhaps not changing around the electrics or plumbing (and perhaps getting some rather odd pipe layouts). TWD 50,000 to 70,000 will of course be more expensive but get a pretty huge improvement in the quality of what you get. Materials chosen have a huge impact on the eventual cost, so it's important to sort out the costs broken down to a very fine degree.
5. Regarding certifications, we made our architect overall responsible for making sure that everything worked and checked out.
Some separate issues that could be good for discussion include disruptive and/or crazy neighbors trying to interfere with renovation projects, how to respond if a neighbor tries to report an alleged "infraction" of their rights, and so on. Many foreigners are somewhat enamored of the top-floor properties which often may have exclusive roof access or even rooftop structures -- and renovation of an apartment can often lead to neighbors coming about to try to assert long-dormant claims to rooftop rights. Even the politics of "building meetings" and how or whether to communicate with neighbors about an upcoming or ongoing construction project is rich grounds!