I think so, but only if there are long posts. Maybe a length of XXXX number of characters of posts per page. The topics per page plugin would always display the same number of posts per page, regardless of length of those posts.
There’s no equivalent that I know of for bbPress. It would be the equivalent of a WordPress blog post page, where you want 9 posts (for example) listed as a default, but if there is a long post, some sort of limit kicks in. I don’t know of a way to do this in WordPress at all, other than limiting the number of posts on a blog page, or with a custom query. The nextpage tag only works on a single long post. It’s possible you could change the number of replies listed in bbPress when it encounters a long post with a tag like that, but I haven’t seen anyone do that yet.