So I'm guessing that you still have a fair amount of time before your exam.....in which case, a few recommendations.
1) Part of building up your test-taking skills is by actually taking tests, so yes, the more timed online practice you do, the better. You'll want to try to do all of your CATs in your course, to really build your time management skills and stamina and make progress. Be sure to then study each exam AFTER you do it to learn from your mistakes under test-like conditions.
2) As you study, both when you review your CAT questions, and when doing other assignments and sets of practice, do try to learn from each question and as Jim mentioned, where possible, try to see how to approach each question from both a "traditional math" approach and an alternative approach (such as some of those Kaplan strategies you mentioned, or just estimating, eliminating, etc). Your goal is to have options on test day, and to develop the ability to decide which approach is best for YOU on any given problem based on a number of factors.
3) Work on timing even for shorter question sets, give yourself approx 2 min/question and force yourself to learn what 2 minutes "feels" like and to move on when you are stuck.
4) Remember that EVERYONE will get stuck at some point, and it's better to make strategic guesses where appropriate and save time for questions you CAN do, rather than trying to do every problem full-out, and running out of time for the last 1/2 or 1/3 or ANY portion of the section. People who score really well will generally have guessed on multiple questions, so reassure yourself knowing that and allow yourself to guess strategically/move on quickly after starting a problem that you really don't see a way forward with. Be proactive with choosing when to guess, instead of being forced to guess for all remaining problems if you spent too long early on.
5) As Jim said, it's less about writing things down just to write things down...some people write a lot, some a little, but no one is looking over your shoulder giving you extra points or partical credit on test day for what you write down or don't. So figure out what works best for you in terms of getting these questions done in a timely way, and use that approach.
Overall, the more you practice under timed conditions, the more you will potentially improve, yes. Good luck to you!!
Jen Kedrowski
Kaplan Test Prep & Admissions
GMAT Teacher
MBA Admissions Consultant
National Product Team Member