The Kaplan review questions are more along the lines of review. The practice tests will be a better example of the actual OAT. I found the Kaplan practice to be a little harder than the real test though so keep that in mind.
I used an mcat physics book which helped me a great deal. The info was a little overkill but when I got to the physics I felt well prepared.
There is a stopping point and instructional area between the natural sciences and reading comp. You also get a scheduled break in between the reading comp and the physics section.
You should arrive about 20-30 minutes early, make sure you bring the necessary identification. Also eat a small but nutritious meal and get some hydration.