I tell you my experience. I'm leveling a priest that it's 60 now and since I have also done some instances (and I have full heirloom set with 20% experience gain bonuses) and been very ahead of the guide, I skipped some zones since they were grey quest for me, well it was a real mess. Missing quests because I didn't to the previous to enable the following. Going in a zone then realizing that I couldn't do that quest because I didn't do the starting quest chain, very unconmfortable. In short what I suggest you it's not to skip areas, or make really sure that you do all the quests required (at least) and check carefully the previous zone you'll going to skip to make sure that you won't have problems with struggling finding where to start the quest chain to sync with the guide section.
The dark side of this disparity is griefing; max level players are able to easily disrupt questing areas in use by players of the opposite faction, and can one-shot most enemy characters. Sadly, even guards in most areas are unable to stand against well-equipped max level players, especially as the current expansion progresses and gear steadily increases in power. Of course, the best answer to this is usually to recruit some max level players of your own faction, or switch to a max level alt, and make the griefer regret the day they flew into Goldshire.
Edit 20 It’s been a week since this post and a lot of people are still reaching out to me with questions which is fine. I have had a few different people reach out to me to help make YouTube videos based off this guide and more info in BFA which I’m more than willing to do. Whoever gets the videos up first I will link them here for you guys to enjoy.