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.).
Anyway I will go ahead & download the Twitch app like everyone's saying, but I still need to know whether my in-game addon settings will carry over automatically, or whether they'd return to default same as if they'd all been uninstalled in the curse client then reinstalled from scratch. Because if it's the latter then I will have to take screenshots of the settings on all my toons BEFORE I install the addons thru the Twitch client.