Do only pr 5 and under links count?

I have noticed with certain sites that have high PR like article sites ect don't seem to show up on a BL level other than 0 with checker sites. Is PR 5 the most you can benefit from link wise?

Backlink checkers will check the PR of the page, not the domain. Often, this will be pr 0. It is the page PR which is important for your backlinks. It doesn't matter if your link is on a high PR8 or PR 9 domain. If it's on a PR n/a or PR 0 page, it's not much good.

There is most certainly no link limit at PR 5.