The way Zygor's works is there is an addon called ZygorGuideViewer that is just a UI addition that displays whatever guide you pick (which doesn't have to exclusively be Zygor's Guides). Granted, it offers some other cool capabilities like auto accepting & turning in quests and selling greys, but these are features that other addons can do as well. ZygorGuideViewer works within the bounds of LUA, which makes the addon itself (and therefore its use) "legal".
My second most anticipated new feature in the Tides of Vengeance update is the Battle for Darkshore Warfront. It’s the second cyclical battle between the Horde and Alliance, in which each faction takes turns gathering resources, fighting in a pitched raid battle and then controlling the Darkshore zone. In what I hope will be an improvement to the Warfronts feature, the controlling faction will gain access to diverse world quests in the zones they control, rather than the “kill x of y” quests from when it first launched.
At the same time, a stat "squish" meant that players' gear level, health and damage were drastically reduced. Monsters' stats were similarly clobbered, though predictably, some lesser-known abilities immediately started one-shotting players. (On the beta servers, a simple toy allowed players to kill each other with one blow, with amusing results; but even on live servers, those bugs were legion.)
War Mode: War Mode can be turned on at level 30 through your talent window, and will give you 10% bonus XP. You will, however, be attackable by players of the opposing faction, but changes have been made so that all players have a fair shot in a fight and even low-level players can kill much higher level players, and at least not get ganked and one shotted. Note: As of patch 8.1, you can get an additional call to arms bonus with war mode on if your faction is underepresented.
The power of items depends on their item level, which you can see on the item's tooltip; the higher the level, the better an item will be. However, the Warforging and Titanforging system - introduced in the Warlords of Draenor expansion - means that almost any item of Uncommon, Rare or Epic quality has a chance to ‘forge' to higher than its base item level: Warforging is up to +15, Titanforging is up to +45.
If you’ve seen or heard people getting excited for World of Warcraft because it’s “getting back to its roots,” thanks to a renewed focus on the shared hatred between the game’s two major factions—Horde and Alliance—in its new Battle for Azeroth expansion, maybe you’re tempted to sign up and give the game a whirl. Or, if you haven’t played in years, perhaps you’re curious to see what’s changed.

Bags: This SHOULD be a no-brainer. The cheap-o version are Netherweave bags, but if you have the gold I recommend you get the largest bags you can afford, since it means you won't have to stop to clean them out as often. In fact, if you have an excess of gold, it's probably not even worth your time to stop and loot mobs that aren't quest objectives. This seems like a small thing, but over the course of 100+ levels, all those clicks to loot add up.

Incursions are a new world content activity that are unlocked when one character has unlocked World Quests. This feature is unlocked account-wide meaning that all characters on that account can access Incursions even without being Level 120. This provides for a lucrative experience acquisition method that is available in a similar pattern to what Legion Invasions offered with nearly an entire level earned by completing an Incursion series which involves four World Quests and one mini-scenario at the end. These also grant item level 370 weapons and Azerite armor, so they should be done any time they are up. Incursions follow a similar schedule to Invasions and are available for 20 hours once they are initiated.

Tiragarde Sound and Stormsong Valley are both fairly similar zones, but Stormsong is a little longer, meaning that you might not even have to finish it to hit 120. Tiragarde also comes with a bit of a warning. There are plenty of side quests to do in the zone after you finish the story quests. Don’t do them. It’s not worth the time or the experience you’ll get.