The truth will shock you! Different people use different words to refer to the same thing. It’s really not that complicated. In Britain, Asians usually refers to people whose ancestry is from the south part of Asia, rather than the east part of Asia; going outside for a fag is something many people do; and the term fanny pack is linguistically amusing.
Specifically on Asians: isn’t the term “Pakistani” tricky because you’re not sure if you’re talking about someone whose ancestry is from Pakistan, or India, or Nepal, or Sri Lanka? “South Asian” is a reasonable catch-all term, like I’ll usually use the term “East Asian” rather than take a guess and label someone Korean or Taiwanese, or “Westerner” for someone here who’s white but I don’t want to assume they’re American or whatever.
Yes. Often. Especially from Spanish speakers. It’s a topic that flares up on forumosa once in a while.