For that time frame, I would skip the national park. I was just there a couple months ago. I was underwhelmed. It's not much different than driving around the Rockies in Colorado, in my opinion, which I have done many times. I was also in Sabino Canyon in Tucson a few days ago and noticed it was also very similar to the Taroko experience.

Yangmingshan is a national park that is just north of Taipei. I've never been there, so I cannot comment on it.

If you decide to go up one of the hills to get some night time photos, please bring a flashlight. And make sure you check the operating time of the transportation option you decide to use.