Though related, this is no longer true. You can now purchase a lvl 90 character boost. Some power levelers have hoped for a day when you could use real money to buy individual items in-game, some times called "micro-transactions." At a Game Developers Conference 2008, Rob Pardo gave a strong indication, Blizzard would not ever go this route with World of Warcraft.
Power leveling is the process of handing over your character to another player (usually it's a seasoned WoW player), who then gets your character to the highest level possible in the shortest amount of time. In essence, someone else does all the hard work for you so that you don't have to waste your time by leveling the character/s yourself. And as with most other MMORPGs, there are a lot of players who offer such power leveling services for World of Warcraft.
As late as possible. Early on, you’ll want to follow the missions in Battle for Azeroth right up until you get the option to send a follower on a two-hour long quest. As soon as you get there, stop doing the War Campaign missions. You can come back to them once you have reached something like 119 and a half and finish leveling with those if you want. If you don’t use these missions to cap off your leveling journey, then they’re the first thing you’ll want to do once you reach max level.
I'd rather not have to manually re-do all the settings for all my addons in-game unless it's absolutely necessary (since I don't have memorized what the exact settings are I use, so I'd have to take screenshots of them all and then remake the settings to match the screenshots). So I'd rather get some more input about this problem before I try troubleshooting it that way.
I've used WoW-Pro for years and in WoD, Legion and now BfA it's been awesome for just going on auto-pilot and working your way through a zone. It has 3 levels of depth you can set, so you can set it to just do 1) the main story, main points of interest and rare mobs and treasure that aren't far off the beaten path; 2) every quest with a more thorough dive into the side stuff; 3) absolutely everything.