Warlocks have received new spell effects; all the other classes received new effects in Legion. Male orcs are now able to toggle between the initial hunched posture and standing upright by using a barbershop, but the other races are not able to toggle between two postures.[5] There are new druid forms for the allied races, i.e. a Zandalari troll forms are all dinosaur-based, while the Kul Tiran humans take forms made of wood and bone as their teachings come from the Drust people who populated the land before them rather than the Cenarion Circle.
I have tried it a few times. It's good if you're new to the game. Otherwise not so much. I found I leveled slower by using it, as it's suggesting to take the longest possible route usually. Basically following roads everytime, when you could take an easy shortcut. Especially if the shortcut involves a bit of fall damage, it's out of question. The "go here" spots don't also update if you take a shortcut, and then the waypoint arrow points to wrong direction. But perhaps it has been updated since then.
The vanilla WoW Horde leveling guide you see on this site was originally made back in 2006 by Joana (AKA Mancow, or FuriousPaul).  The guides have been tweaked many times over the years to make things "faster".  The leveling guides were made because of all the messages I got from people asking me how I was able to level up so quickly on new realms.  I was first to level 60 on 7 different realms (3 with Mancow and 4 with Joana), even winning Blizzard's "First to Level 50" contest they held back in 2006.
Buffs. Food/Flasks/Scrolls/Potions/Elixirs are a small, but noticeable, buff to your killing speed and survivability. If you have a max level character that can already supply you with cooking or alchemy, you'll be very well off, because the AH is a cesspool for this. I can't really give you specific foods or potions to look for, since each AH is going to have different supplies. Generally speaking, lower level foods are going to only last 15-20 minutes until you can buy the more powerful versions at 60+. Look for anything that adds versatility or your primary stat, and buy stacks for each level range(1-60/70/80/90/100).
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.

As you can see, both of the guides contain quite the same features. The only exceptions being Dugi Guides does NOT have Gold Guide but it is a slightly cheaper choice. Also when using Dugi Guides, you can choose the difficulty level for the guide; If you want to level up at a faster rate but with higher difficulty, it is an option with Dugi Guides but Zygor Guides does not offer this and instead you will be forced to manually choose higher level guides if you want to skip the guide recommendation.
I used Zygor for legion and BFA, used AA on an alt for BFA. Personally i like Zygors format more. I like being able to target things like achievements. I used Zygor to get my Mindworm and my Lucid Nightmare as well as finish the Rep grinds for the allied races. I have zero complaints. My experience was great. I also used Zygor for some professions, recipe acquisition, a couple mounts, all of the Suramar quest line. Thank God for that. And for the last zone of Draenor on my Demon Hunter.. i forget the name.. Whatever the big daily hub thing was called.
Despite the fact that World of Warcraft still relies on the old 14-year-old game engine, the game can cause some frame rate drops even on newer hardware equipment. So we've decided to devote a lot of time and space to answer such questions like: How to set up the graphical options? What should I do to make sure that WoW runs smoothly? WoW's hardware requirements have evolved over the years due to graphical improvements, so find out if your computer can handle the highest graphics settings of the game.