Whilst we can’t give financial advice, I’d say this though. Hong Kong is quite a different market and the use of credit cards are less common compared to other alternatives such as the Octopus card.
Hong Kong’s credit cards are much less lucrative compared to Australia or the US. In fact, it is more like Europe where credit card rewards are more restrained and controlled.
If you are looking for a rewards credit card to earn frequent flyer points and the like, look for the big banks like Heung Seng, HSBC, Standard Chartered, Citibank, Bank of China or AMEX. So far, the only credit cards that directly earn frequent flyer points are the AMEX Asia Miles cards or Bank of China cards for earning Hong Kong Airlines frequent flyer miles. Other big banks have a variety of flexible currencies that you can transfer to other partners.
Hope the above was helpful in helping you look at the options you have. I’ll remind you though that credit cards aren’t a big part of the culture there as people usually pay by Octopus card especially for small purchases like coffees.