We don’t have "Which ’wich" in the UK, but the best subway I have had was made for me in a little sub shop in Cardiff Bay.
However if you want unbearable confusion, try ordering a ‘pastrami on rye’ deli-sandwich in New York. I was offered a choice of 6 rye breads, three spreads, two types of pastrami, 4 types of salad, five or six types of dressing, two types of English mustard, and three ways for the sandwich to be wrapped. Thank fully I stumbled through that, but was thrown by the number of ways my black filter coffee could be made, served (4 or 5 I think).