People from noakhali look just like any other Bangladeshi, you can only find out they're from Noakhali when they try to speak Chattgaiya in their funny accent but they do speak it pretty well for the most part or if they speak Noakhaila language.
Speaking from my personal experience and what I've heard from my elders : A vast majority of people from Chittagong city have foreign ancestors due to our exposure to foreign traders coming to trade at the port. I myself have an Afghani Great grand father. We have a locality called "Firengi Bazar" where the locals look slightly fairer, they're the descendants of Portuguese sailors and merchants. Anyway back to the point my elders allege that WE (people of chittagong) are lazy and only live by selling ancestral land (This is true in some cases including my uncles who have never worked a day in their life) and people from Noakhali who often come to CTG as labourers and workers then buy this land.
I don't know if noakhailas are rich but they're very self sufficient and often help each other out this is most evident in middle eastern countries where they have their own help groups. Also if you take a survey of any 10 Bangladeshis in Kuwait, UAE or Saudi Arabia 4 to 5 will be from Noakhali as they like coming to middle east for making money.
Nobody really knows how it started but people from Feni+Noakhali and People from Chittagong have been entangled in a senseless race or competition, they claim to be "Golden District" and we rebuff their claims and on it goes. However now many men from CTG are marrying women from Noakhali and overtime this "animosity" will end.
The competition I speak of has been showcased in many telefilms and Dramas, all in all its mostly just friendly banter :
I watched a video about these Portugalise descendants, they are a very small community, correct me if I am wrong but I think most of them are christian.