How to figure out if regulation allows imported fuses that are higher quality than what is legally required, but is not readily accessible?
Type B only affects the magnetic-trip overcurrent portion of the breaker, designed for detecting short circuits. It doesn't affect the RCD part of the RCBO, or the thermal part of the MCB. 

Using Type C breakers is fine unless you have such a long run of thin cable that there isn't enough fault current available to trip it at the far end. Hong Kong codes should force using either a smaller breaker or type B breaker in these cases, but usually volt drop will cause people to use a smaller breaker first.

Using a type B makes you more likely to suffer nuisance trips from motors starting, inrush current from switchmode power supplies (turning on a bank of LED lights can be a serious issue for this), and other similar issues.

Unless you have circuits over 50m in length, according to my copy of AS/NZS3000 which is likely similar to your rules, in most cases Type C is fine.

Commercial vs residential doesn't play into it.

I can't comment specifically on Hong Kong code.