Where I live homeschooling is more a proactive family / philosophical / lifestyle choice, rather than a reaction to a negative school environment, so we don't get much of #1.
The commonest situation is #2 here. We have an exceptionally flexible local public high school that works very hard to serve the needs of homeschooled teens on their terms, should they choose some formal schooling. And most of them end up doing so at some point. My ds14 will likely start attending a bit of school next month for the first time ever. He'll probably take one or two courses in class, take part in field trips and electives, and they'll give him credit for much of his out-of-school learning. This sort of approach has been a good mix for my eldest dd over the past three years.
In the local homeschooling community we have found that the school administration and the peer community have been incredibly welcoming and supportive of our kids as they've entered the school system. Even the students who have significant lags in certain academic skills have felt very much appreciated for the skills and perspectives they do have.
I know only a couple of homeschooled kids who have not eventually made any use of our high school's offerings. We have no college or community college here, so that's not an option. Most teens seem to enjoy availing themselves of some formal education out of home at some point and for us the high school is a great option. Our situation, and our school, are quite unique though.