Exhange here or overseas?

I have to go to Hong Kogn then Mainland, will I get a better exchange rate in each place?
I understand this has been discussed before, ususally I believe exhcanging when you get to a place is best but with New Taiwan dollars being a ‘minor’ currency I am not so sure.

From what to what. I got better rates US to NTD in Taiwan. Megabank in particular

Thanks but I need the NTD - HKD/RMB in particular