As a South-Asian Muslim myself, I find that the less there South-Asian Muslims there are, the more they 'integrate into society' as you like to call it. I mean in terms of my friend group I have Christians Hindus and Atheists all in one group and we don't make a fuss but I can't say that for everyone. In terms of marriage, I guess it's just a matter of how hey were raised and personal preference as I know that many of us tend to marry those who we're more familiar with in terms of culture as many may fear it would be difficult to integrate their ways with their spouses of they were to be of a different culture. I reiterate that I am no expert in this and that this is just from my general knowledge of this.