If you have given your best in GMATPrep mock then getting a 700 is bit difficult in actual test. +/- 50 points of GMATPrep will be your actual score. Its better to reschedule and prepare.

I didn't give my 100% since I only had 2 hours to do it I had to rush some answers.

Give another mock or repeat the same but make sure you take with essay and with 8 min breaks if necessary, then decide on what you can do. Try to simulate the testing experience as much as possible and give your best.

I think going from a 590 to a 700 in so little time would be difficult, but not impossible. You haven't told us anything on which books you've been using and your quant/verbal split (which one you're least comfortable with). Maybe share that info so that we make more informed recommendations?

I have been basically studying from material I got during the course, but now I have begun with the GMAT verbal review and today I'm starting with the Kaplan software. For Kaplan I got a 630 in my diagnostic test with a 36/41 split.

Thanks!

Then focus intensely on quant to get your score up! If you're interested in the best books for quant out there, check out the Manhattan GMAT Number Properties and Word Translations guides.

The bigger the hoped-for jump in score, the more it depends on why you're getting the scores you are. Jumps of 100 are certainly plausible in a couple weeks, but in my experience they come more from significant content gaps ("oh! Now I understand how triangles work!") rather than processing ("Oh! Now I have made a 10% reduction in careless errors"). The exception is when people go from skimming RC and CR to reading the prompts carefully -- there is usually a significant jump in score when people start "doing it right the first time" (if they weren't doing so initially).

Which is the most reliable (as in the closest to the actual GMAT) mock test: GMAT prep, Kaplan CAT, Manhattan, Arcos?

It changes from edition to edition; yet another reason not to try to track your progress by means of the projected scores.