OAT Achiever vs TopScore? Any more practice ???

I am a terrible test taker so I am trying to take as many practice tests as possible. I took the Kaplan ones that come with the course (they only give 5 practice tests). I wanted to know of any other places I can have access to practice tests. I want to take as many as possible. I've heard of Topscore and Achiever, one is better

Also, is there any book that is only practice exams?

Thanks,