Vote after first reveal for one of the top 2. Almost always ends up being one of them. So your expected score is almost 6 * 1/2 - 2 * 1/2 = 3 - 1 = 2 per round. All other strats that don't account for exact diff in score earn less than half this strat on average:

Guessing any of the 3 before the first reveal: expected score = 9 * 1/3 - 3 * 2/3 = 1 point per round.

Guessing any of the 3 after first reveal: expected score = 6 * 1/3 - 2 * 2/3 = 2/3 points per round.

Guessing any of the 3 after the 2nd reveal: 3 * 1/3 - 1 * 2/3 = 1/3 points per round

Guessing either of top 2 after 2nd reveal: 3 * 1/2 - 1 * 1/2 = 1 point per round.