Option 2, though I am under the impression that this forum has a disproportionate number of people having mothers who kept their name.
I've always been under the impression that this forum has a disproportionate number of people having mothers who moved the position of their original surname to become their middle name.
Those are the only two options in my family. Like, if your name is Joan Alice Taylor and you marry Steven Walter Smith, you can still be Joan Alice Taylor or you can become Joan Alice Smith. Those are pretty much your two options in my family. Some choose to keep their original surname and some choose to change it. My mother changed her name. My wife kept her original surname. My sister changed her surname in one of her marriages but kept it in another marriage. None of them moved their original surname to the middle-name position. That just isn't done in my family.
What always struck me about this forum is that there seems to be a large number who make their original surname their middle name after they're married. Like, if your name is Joan Alice Taylor and you marry Steven Walter Smith, then you become Joan Taylor Smith. As far as I know, no one in my family has ever done that. They either stick with their original last name or they co-opt the husband's surname. Nevertheless, it seems fairly common based not only on this forum but from what I've seen in general society. I have always found the concept of co-opting the husband's last name and moving your original surname to the middle position very strange. In fact, I'd never even heard of it till I was a teenager, and my mother explained to me that it was somewhat common in society. Since I've been posting here, it seems to me that it is the norm on this forum, even though to my knowledge no one in my extended family has ever done that. They either keep their last name original or they change it.
My situation is somewhat different. My wife's mother was given no middle name, so making her given last name into a middle name was more a matter of adding the new name to the end of a short list. My wife was given her mother's maiden name as her middle name and her father's last name. She kept that name.
My children were given a unique first name but their mother's middle name and my last name. If my daughter chooses to maintain that tradition then the same middle name would exist through four generations through female ancestors. In principle the pattern could be maintained through female descendents much as a patrilineal last name is through male descendents.