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.
This level range opens a variety of zones from the Cataclysm expansion, which are spread across the game’s original continents, but it’s more efficient to head to the continent of Pandaria. You can spend the entirety of this level range exploring its uniquely themed zones and quests. The Jade Forest, Valley of the Four Winds, and Kun-Lai Summit are our picks, but all the zones are worth checking out.
He then added, "There is another issue tangentially related to this discussion that I also would like to address: Many feel that it takes too long to level in the 60-80 range in particular, and that the combat pacing issues discussed here are just a piece of that larger problem. We agree – currently players are taking about 15% longer per level, on average, in that range as compared to before 60 or after 80. We’re in the process of assembling a set of changes that will smooth out the experience curve at level 60 and beyond, reducing the experience requirements for those levels."
From my experience on the Beta as an enchanter/tailor, scrap every trinket (and maybe rings). Trinkets seem to always give expulsom and it's needed in the higher enchants. Scrap any cloth green drops for the extra cloth, but other gear and blues and purples disenchant for the mats. The scrapper seems bad at the return on some items. I'd scrap old Azerite armor and get some cloth and a bit of thread.
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