If you are not joining a guided tour, here are a few videos you can watch beforehand about Taiwan for your reference! All these are based from the six-day itinerary I wrote the last time at post:
Things you have to know before visiting Taiwan
Taiwan travel tips
Taiwan vacation travel guide. Note: This video is owned by Expedia.
Guide to Taroko Gorge
Guide to Jiufen
Yehliu Geopark Travel Guide
Maokong Night Market in Jeelung
Chiang Kai Shek Memorial Hall
Exciting Ximending Shopping
Sun-Yat Sen Memorial Hall
National Palace Museum
Comparing Two Palace Museums
A Tour of the Shilin Night Market
Beitou Hot Springs Guide
Amazing what Youtube has on offer, right? Good luck!