As far as I could juge there is the buffet pay the weight ( we were too late for that) and the take away choice that you can also eat on the site. Soup in a big drum for free.
Lonely Planet claims more or less that this is the best veggie in Taipei.I would not say so. But, fair food, low price and above all: veggie. If you are in the neighbourhood, it is not a bad choice as you might not find another veggie.