I am using the "one post per page" and the tree at the bottom.
I also tried in the past the other options, but this was the best for me, as I can focus on the post I read and by just a click I can read the post that is answered (if I wish in an other window).
I also tried in the past the other options, but this was the best for me, as I can focus on the post I read and by just a click I can read the post that is answered (if I wish in an other window).