-Island Expeditions- Island expeditions was one of the new features I was looking forward to but Blizzard no longer makes games that are ready when they are ready but rather makes games ready when the deadline comes. Thus, many of the new features are completely stripped down from what was expected and it's literally just a small scenario you enter with two other players to continue to grind out your Azerite neck piece.
Like I said, engineering is the best when you aren't worried about making gold. The Loot-a-rang is super useful, nitro-boosts are nice when they don't fail, and the glider cape enchant is nice too... you get wormholes to Pandaria, Draenor (make sure you have a glider), Legion, and Argus (as well as a couple old world teleport locations)...Jeeves (and to a lesser extent Reeves) and MOLL-E are also super useful (bank and mail access anywhere, repairs, etc.).
Mythic+ rewards will also go up by 30 item levels; however, during the first week of Season 2, rewards from end-of-run chests will be capped at Mythic 6 quality (item level 385), and the chest you open next week will contain Season 1 rewards if you do a Mythic+ run this week. (So, for example, if you do a Mythic 10 during the final week of Season 1, you’ll get a Season 1 item level 380 piece and 60 Residuum from your first Season 2 chest.)