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.
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.