Change at Bank of Taiwan/Mega Bank in Airport - 30nt transaction fee (23.55, 24 Dec)
Change at Bank of Taiwan in town - no transaction fee (23.38, 31 Dec)
Change at DBS in town - 1% admin fee (23.78, 31 Dec)
Change in SG - no transaction fee (23.35, 22nd Dec)
*in brackets are exchange rates observed on different days during my trip
There's no best option I feel. If u change at DBS, the 1% fees will push down the exchange rate and in the end it works out to be the same as the rest. However, rates in Taiwan were definitely better for me, just minimally. I guess if u are lazy to change in sg then do it in Taiwan airport. Once u are out of airport, it is rather difficult to find a bank that accepts sgd.
In my case, I was in Taichung and DBS was far away so I was walking around trying to find any bank that takes in sgd. First time round, I circled 3 banks, in the end changed my leftover hongkong dollars in a small Bank of Taiwan branch. 2 days later, I had some time left before moving on to Taipei, so I circled 3 more banks before I found the large Bank of Taiwan which accepts sgd.