Even though a modern server architecture is used, Classic servers won't have the same features that current World of Warcraft does. There won't be cross-realm servers or Looking For Raid and Dungeon Finder automatic party matchmaking. There are still a lot of questions about how the team will tackle it. This endeavor is being undertaken by an entirely separate team at Blizzard from the one working on World of Warcraft and its next expansion.
You will have to talk with flight masters in most towns or cities you visit in order to gain access to that settlement's flight path. Flight masters who have a stop you have not yet unlocked will have a green displayed above their head (and on the mini map), much like a NPC with a quest. Unlocking flight paths as you progress through various zones will allow you to pay for a quick ride to a destination you have previously visited. This method of travel is significantly faster than walking or riding a mount.
Some even more advanced gold makers might also attempt to monopolize the market. It’s fairly easy if you have quite a bit of gold – just buy out every single item on which you want to have a monopoly on and then reintroduce it to the auction house with your new (and higher) price. However, it’s worth mentioning that monopolization tactic is risky business practice. But where’s high risk – there’s high profit.
I am currently working full time on my Vanilla WoW leveling guides. Soon there will be a 1-60 speed leveling guide for Alliance, along with in-game guide versions available for my members area. As of right now, there is no members area, but if you would like to show support for my efforts into this project, you can simply donate to me via Patreon if you like (you will get some cool rewards in return). Or you can donate directly with PayPal if you like. All donations are highly appreciated and they will only motivate me more to continue making the best vanilla WoW leveling guides on the web.
All the work we’re doing will ultimately allow us to recreate an authentic classic experience on a platform that is much more optimized and stable, helping us avoid latency and stability issues. Additional improvements will include modern anti-cheat/botting detection, customer service and Battle.net integration, and similar conveniences that do not affect the core gameplay experience.
What add-ons can do has changed over the years and have become much more sophisticated as authors have gained years of experience and savvy. We’re not 100% on a concrete solution to what this means for WoW Classic yet, but one thing we know is that we’re not going to roll all the way back to the 1.12 add-on API. Doing so would open the way for nearly complete automation of combat decision making allowing for “bot” behavior that is counter to the core WoW gameplay experience. This is one thing we know we don’t want. On the other end of the spectrum, the modern API offers some additional functionality for creating social features that could also undermine the authentic classic experience. We’re still figuring out the details and looking for a good middle ground. We’ll be keeping a close eye on feedback from the community and add-on authors on where we should be setting those boundaries.
Blizz stated in a watercooler that they're using the 1.12 database as a starting point. I don't think it's a stretch for people to assume that most game features and mechanics will be in their 1.12 state. The kind of stuff I would expect to see reverted would be numerous AV changes, but I seriously doubt class mechanics are going to be reverted. I'd be surprised if the threat changes that ruin pre-naxx encounters are reverted.