There has been a thread previously where cost of IB was compared to local brokers in Japan and IB was considred more expensive. However, those local brokers only offer web-based interfaces and of course only in Japanese. Customers must be residents of Japan when they sign up. And short-selling of stock is not allowed.
I'm pretty sure OP is not Japanese, currently located in Europe and looking to trade Australia/Japan next to European. But I'll look up that thread!
I think that interactive brokers are in a domain position. But it should classify customers as active traders and custody traders. However, even looking at the competition you do not notice advantages especially for the lack of API. Degiro I do not know if you go through someone (as i imagine) or have a direct connection with the asian exchange. (I do not see it in the list of participants in the exchanges)