The whole reason this forum exists is precisely because the OG explanations are often too formal and time-consuming for most test-takers! My advice: always make sure that you understand each question you do so thoroughly that you could solve it multiple ways. You'll only need one that works on test day, but the more tools you have in your toolkit, the more likely it is that you'll have one that works when you need it. If those tools come more from forum explanations than from the OG, that's to be expected.

The truth is that what you need to be doing is learning how to come up with simple, efficient, fast ways to answer questions.

That's what the GMAT is about, testing your skill in coming up with ways to use the resources at hand to solve something.

So, ironically enough, the explanations in the Official Guide are maybe good for explaining why an answer is right while not necessarily being ways that one would actually handle questions on the test, and often the best, fastest way to handle a question will involve doing something, such as plugging in answer choices, that the Official Guide would pretty much never suggest.

So these forums tend to provide much better ways of handling problems.

As importantly, they also provide a forum for you to see not just how to solve specific questions but also how people who are good at handling the GMAT come up with ways to figure out the answers, and that's key because the GMAT is not really a math test that you will rock just by learning specific formulas or strategies, or an English test that you can easily rock just by learning a bunch of grammar rules. The GMAT is a test of how good you are at on the fly coming up with a way to handle a question, possibly one rather different from any you have seen before.

The baseline is that you have to mark the questions correctly on the test.
If the forum helps you in arriving at the right answer in an easier way, then why not

More over, you can look at the answer provided in the OG and then come back to the forum. This might give you additional understand of some concepts or problems and that can come handy on the test day.