Noob with lots of questions

Sorry, I'm brand new and wanting to figure out how this works before I settle on a realm/server.

I know it says on Frostwolf (MoP) that there is a x7 rate for XP, but is there a way to lower that back down to x1?
Is the AH active at all (can I make gold off it)?
If not, how do I go about purchasing gold?

I thought I saw something that says that you can Transmog on the Wrath servers?? Did I read that right?

Can we use addons? If so, would I be using Curse/Twitch or is there a special program to be used?

No, there isn't
Can't comment too much on AH as I don't play it, but looking that there's under 300 online atm the're must be some sort of activity there, be it not much.
You can buy gold from players in the trade section found in My Account > Trade ( you need to be premium and have 2fa enabled for 3 days straight to access it)

Yes there is transmog on Wotlk, http://forum.warmane.com/showthread.php?t=342913

Yes you can , but you need to install them manually and ensure the addon is compatible with the patch your playing , I'd recommend downloading them from pre made guides on forums
http://forum.warmane.com/showthread.php?t=51521
http://forum.warmane.com/showthread.php?t=378191