Forest and County are unusual in having such good relations. Can throw Mansfield in too. I guess not having spent much time in the same division helps.

If you grow up in a small town/village you’ll normally support a big (league) team plus the local non-league side. How often you actually go to games varies by a lot of things - not least the cost. Also a lot of people work Saturdays and Sundays now which restricts things.