The most accurate predictor of your actual GMAT performance is the GMATPrep. Make sure that you take the CAT's under the same conditions as you would for the real test.
The OG books are necessary, but probably won't bring you to a 700-level score. There are simply not enough hard questions in those books. But if you're scoring above 90 percent accuracy on the first try with OG Quant questions, then you're in good shape. Once you successfully complete the math problems found in the OG, immediately move on to the
GMATClub Tests.
Don't stress yourself over what score you might have right now. Just focus on answering the OG questions and learning from your mistakes.