Every server currently being used will be upgraded into TBC servers. You can open new Vanilla versions of these servers. You can choose to activating your character on the Vanilla or TBC version. You'll need to pay if you wish to WOW TBC Classic Gold activate the same character on both.
Edit The article is taken from Blizz. On the day of patching, you'll be able to open Battle.net desktop and choose the game you want to play: WoW Classic or Burning Crusade Classic. Both games will show your characters that are currently playing under the old name/s of the realm. When you have chosen a game, choose a character that you would like to play and then confirm. You may also use an optional paid service to play the cloned character in the two game types if you choose to play as your character on both. All you need to do is sign in the game as usual and begin playing.
Since the copy has been completed prior to release Yes. Classic includes all characters, therefore there is no delay in copying if you select Classic. TBC can cause delays, simply because it's not immediate. It can cause more characters being copied simultaneously. This could result in the system being unable to function properly.
Bots will likely benefit from buy TBC Classic Gold the boost, which makes it more difficult for bots. If bots were controlled and the boost was controlled, it wouldn't be an issue. My family and I go back to classic because we enjoy the tbc. They join only because they have the ability to increase their levels.