The difference in Cantonese usage couldn’t be more stark. I’m currently in Hong Kong. Everyone speaks Cantonese, and if you speak Mandarin, that says to people “This person is a Mainland tourist, let’s overcharge them.”, and if you speak English, that says “This person is a rich foreigner/white person, let’s overcharge them.”. This is despite English and “Chinese” (both variants) being official language in Hong Kong. All Government services are provided in all three languages but if you use anything but Cantonese, you’re going to see significantly more friction and encounter many more difficulties that Cantonese speakers don’t.

to be fair it’s like this in almost all regions where the locals speak a minority language and they try to preserve it. In Canada they have english and french as an official language but if you try to speak english in quebec they will not be happy because of their history with the language/anglophones. you are seen as a form of colonizer if you speak a non-native language (both in quebec and in hk)