Capital: Taipei – where night markets
Transport: Trains are very efficient and there are also many bus links. Bus can be sparse in rural area. When in Taipei, a must have is Easy Card to get around.
Currency: New Taiwanese Dollar (NTW). 4 NTW = 1 HKD, 125 NTW ~ 4 USD
Handy apps: Google Translate is your friend as more places than expected won’t have English. Google Map works quite well in Taiwan as well but you likely need to use local website to check regional transport time table
Language: Taiwan speaks Mandarin but uses traditional Chinese characters (like HK and Macau). Knowing some Mandarin can really help