For the 2nd week of BFA, M+, Raids, and Rated PvP are still not open so there isn’t that much that you have to do. Do your Island Expos to level up your Heart of Azeroth, do WQs for rewards, do Warfronts and the 11 weekly quest turn ins, and run your Mythic Dungeons again to try to get the most gear before reset. I personally will be spending a lot of Week 2 farming mats for consumables for M+ and Raids but whatever you choose to do is up to you.
If you level with friends Prot would probably be the way to go so you could pull and face tank the packs. I leveled 2 pallies both ret on beta and had 0 issues. Selfless healer and wake of ashes work absolute wonders. I leveled a bit as prot and just felt like I did 0 damage. I leveled solo so I don’t know about the xp fall off but I would assume it’s the same as legion.
Was doing it at 52 on my lightforged paladin and it was easily the slowest zone out of the ones I'd done. Granted, I didn't have War Mode on so I didn't have any PVP talents, but it felt like about 40% of my time was spent waiting around for respawns or wandering around looking for mobs to kill to get a quest item that had like a 5% drop rate. Maybe I just got unlucky but I definitely won't be going to that zone again for future heritage armor runs.
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