Study Plan Question

Unless your timeline is condensed (e.g. you have to take the GMAT in a month), covering every single topic beginning-to-end is recommended.

However, there's one very important thing missing from your study plan: the Official Guide! Reading strategy guides will tell you how to approach GMAT questions, but the only way to test whether you're absorbing that learning is to practice with real OG questions. If you haven't already, buy a copy of OG 13th edition (older editions are fine if you have them, but if you don't have one yet, might as well buy the new one).

Make sure that you're practicing OG questions topic-by-topic. For example, after you read the chapter on Ratios in the MGMAT Fractions, Decimals, & Percents Guide, flip to the back of the book where it lists all of the OG problems by topic. Then do a handful of ratio problems in both PS and DS. For each topic, you want to reinforce that learning by practicing on OG problems that directly relate to the topic, rather than reading the books cover-to-cover and practicing OG problems at random.

It's also critically important that you track your work - what you've gotten right & wrong, and how long you've spent on it. That way you'll know what topics to go back and review.

Good luck!

I agree with ceilidh,

One topic at a time is the way to go, as is keeping an Error Log (aka Improvement Chart) while completing questions from the Official Guide (OG).
If you're interested, you can find a free downloadable Improvement Chart here: https://www.beatthegmat.com/mba/gmat-error-log. This will help you identify and strengthen your weak areas.

You might also consider signing up for BTG's free 60-Day Study Guide: https://www.beatthegmat.com/mba/gmat-guide. Each day you will receive an email with a series of learning activities that will guide you, step-by-step, from Day 1 to test day (an outline of all 60 emails is here: https://www.beatthegmat.com/mba/gmat-guide-outline).

This will ensure that you will cover everything that the GMAT tests.

Cheers,
Brent