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.
Currently, it is believed that the War Mode rewards will change depending on which faction is more heavily prevalent with War Mode activated. The Horde have typically had more participating in War Mode, so the reward has been increased for the Alliance to incentivize more participation in War Mode. These rewards could potentially be increased to both the Horde and Alliance to incentivize both factions to higher amounts of War Mode participation.
Kul Tiran human (8.1.5) - "Kul Tiras was founded by fearless explorers who sailed uncharted waters in search of adventure. As a key member of the Alliance of Lordaeron, the Kul Tiran navy dominated the seas of Azeroth with its legendary fleet. But after years of turmoil and hardship, the kingdom grew isolated and vulnerable to dark influences. Thanks to the help of brave heroes, House Proudmoore has been restored and Kul Tiras is poised to fight alongside the valiant Alliance once more."
At 98 you have the option to drop what you're doing and return to your capitol city to start the quest for your Legion Artifact weapon. However, I do not believe this is necessary to do right away unless you're struggling with kill speed in your current gear. I would recommend waiting for a natural pause, such as hearthing to repair and clear your bags. From 100 to 107 you won't even really fight mobs that often; only just enough to clear the way to any treasure you need to pick up.
Also get the Heirloom Mount. Being able to have basic riding speed from the beginning will save you a lot of time if you're starting from level 1. Allied races start at 20, so this is a non-issue for them. It's important to note that Pandaren can not use this mount until they finish their starting zone and pick a faction. Being Horde or Alliance is a requirement of the mount.
That lack of storytelling agency may soon change with Patch 8.1, Tides of Vengeance, which is coming to Battle for Azeroth soon. While there are plenty of fun gameplay changes that should make the expansion better, one of the most interesting additions is that of choice. In an upcoming quest, players will be able to choose whether they want to support Saurfang or Sylvanas — essentially honor or evil — in the struggle for Horde warchief.