This Pad Thai recipe actually originated from Bangkok, Thailand and comes from testing hundreds of different variations from food carts all over the city. Pad Thai is the pinnacle of street food. While "street food" may sound dirty and unappetizing , food cart cooks are in such competitive situations. Due to the circumstances of having limited space, ingredients and tools, they need to specialize in a dish or two just to stay in business. These accomplishing cooks have cooked the same dish day-after-day, year-after-year, and consistently perfecting this dish.
The ideal Pad Thai is dry, light bodied, fresh, complex, and balanced flavor. It should be reddish and brownish color and not bright red and oily like I've seen in the US. The ingredients listed above can be somewhat frightening ,but many are optional. If you would like to make authentic Pad Thai, just like in Thailand, then use all of these ingredients.
Alternatively, Pad Thai is a perfect vegetarian dish, just remove shrimp and replace soy sauce for fish sauce. Add more tofu if you want.