Add to the list: The Hollywood Brown Derby!
Yes, all signatures require 2 TS credits.
If you're on the regular DP, and want eat at a few signatures, you might save money by paying OOP for the signature meals.
Say you book a dinner at California Grill. I would use the CS credits for breakfast and the TS credit for lunch that day.
If you plant to eat at several signatures, you may be better off getting the Deluxe DP or just not doing any DP.