Congratulations on reaching Level 120! There are a myriad of new things to do. The first thing you should do is head to your faction hub ship where you have been doing your mission table quests and footholds to pick up and complete the quests necessary to unlock World Quests. World Quests will provide you an opportunity to grind reputation levels, acquire gear, and gather Azerite. There are tons of new things to do that we will cover in our Level 120 Battle Guide found here: Level 120 Battle Guide

I defintely think at 118 you should go and do all four of these parts. These are required to unlock World Quests and probably take about 60-90 minutes to get through. If you do these whilst levelling (especially all in one go at 118) then when you hit max level you're ready to go on WQs. You can go finish the zones quests at your leisure over the next weeks/months or never even finish them if you don't care about questing.

Auto looting a mob will increase leveling speed for the expansion. to enable it = Esc, Interface, Controls, Enable Auto Loot. I'm including this because sometimes the simple things are missed. I, sadly, went 3/4 of the way through WoD not knowing that hitting the space bar for my mission tables is much MUCH faster than waiting it out. (i never claimed to be smart OKAY) =P

Before you begin, you must decide on whether or not to enable War Mode. War Mode makes it so that you will only see other players with War Mode enabled, which also enables PvP activity. Note that if you are in a party with someone not on War Mode while you are, you will be unable to see him or her. War Mode provides an experience buff as well as the enabling of three PvP talents that will greatly increase your power. Regardless of whether or not you enable War Mode, your objectives will remain the same in that you must complete all quest content to unlock flying later on and many of your War Campaign and Allied Race requirements. War Mode enables 10% bonus experience, 10% better rewards from World Quests, and allows for the gathering of Conquest points which can be used to buy gear. If you do play on War Mode, it is recommended to play with friends. Leveling without War Mode will not be significantly more time consuming.
The additional recipe ranks can be obtained either by exploring the outdoor Broken Isles zones or as rewards when you dive into the dungeons of the region. If you’re feeling up to the challenge, you can aim to hit skill level 100 and player level 100 to open up profession world quests, which rewards higher rank recipes for your Legion gold making operation.
If you bought Legion and have no desire to go through old content, good news! The new expansion comes with a free boost to level 100 for one character. You can buy these boosts from the in-game store whenever you want, but they normally cost $60, so savor this free one. Use it for a class that you are confident you will enjoy. As a fresh level 100 character, you will be able to immediately begin the quest that takes you the Broken Isles, the new region where Legion takes place.
Heirloom experience should be boosted, now that zones scale. If a zone scales along with me, it shouldn't matter if it gives me 20 levels instead of 10. I'm still enjoying the experience, even as a veteran player. I don't need to see every zone on every character again; that's the point of heirlooms. I can still enjoy the leveling experience, and the scaling, and the full outdoor experience of the zones -- and still get to the end game content I enjoy in a somewhat reasonable time as an employed adult. And the change wouldn't affect new players.
To put that in perspective, the high-priced vanity mount released with Legion is a giant spider called the Bloodfang Widow. It costs 2 million gold. If you wanted to buy one with cash, using WoW tokens, it would have cost over $1,100 at the time Legion was released, in August 2016. If you wanted to do the same thing in July 2018, it would have cost less than $200.

How many hours will players grind for a token now worth $15? On the Chinese and European servers — which include Eastern European countries where minimum wages are less than the equivalent of $2 per hour — there are plenty of people willing to sell their time for these prices. There is more of a question of relative value in North America, where players tend to value their time more highly relative to subscription costs.
Common methods of power leveling include doing only those quests which are most efficient in terms of experience over time, and analyzing the quests in a given zone so as to do them in the most efficient order possible. Remember, the idea of power leveling is speed and efficiency--you may wish to obtain an addon that will show you how much experience per hour you are gaining to test your techniques. Additionally, ensure your character's talent build is crafted for maximum endurance. You want as little downtime (walking, drinking, eating, crafting, typing, etc.) as possible.
“I think [the levelling experience] is a pretty hotly debated topic internally, about how to handle that,” Dawson said in a recent interview with Gamesindustry.biz. “I think we recognize that we’re not giving new players as good an experience as we can, and we do want to focus on how to make that experience better. There’s 15 years of content that people should have the option to do if they want to, but we also want the ability for players to play with their friends quickly. That’s why we developed things like the boost [which automatically raises one character to an appropriate level for the current expansion], which you get if you purchase the game itself. The scaling tech was also a way to help us do that, and you can sort of choose your own path through expansions and story content.”
- Right to restriction on processing. If there are grounds for restriction on processing, for example if you contest the accuracy of your personal data, it will be stored and processed otherwise only if you consent or to exercise legal claims, or for the protection of rights of another natural or legal person. If we have disclosed the personal data in question to third parties, we will inform them about the restriction on the processing of the personal data, unless it is impossible or involves disproportionate effort to do so. We will inform you before the restriction is lifted. 
×