I am a new player joining TBC, I'm wondering if i can play at a lower rate than 5x of Outland, Say 2x so i can have a decent amount of fun while leveling up..
If there is a feature like this, how do I activate it? If not, will it be implemented, since there's no normal leveling server?
There is no such feature. There have been suggestions to add it but doesn't seem like it's going to happen. On website under services you can find experience lock feature. It will stop your char from gaining experience. It's there since it did not exist in game in TBC. You can enable it when you want to stay the same level for some time. That's closest you can currently get to what you are asking about.