Rule 10 says players “change ends at the end of each set, unless the total number of games in the set is even.” A 7-6 set score is always an odd number of games, so you change ends. Therefore, you finish the tiebreak on one end, and then start the next set on the other end.
Who should serve?:
Rule 5.b says that “the player/team whose turn it was to serve first in the tie-break shall be the receiver in the first game of the following set.”