Should I intend to pray Tarawih, or Shafa’ and Witr in the last three rak’ahs of Tarawih? And what is the ruling if I only intend Shafa’ and the Imam combines Witr with it?

The Witr is a specific prayer that requires a distinct intention at the beginning of the last three rak'ahs of Tarawih, and the two rak'ahs that precede the single rak'ah of Witr. The Witr can be performed with one salaam or two salaams, and both are permissible.