It is worth mentioning that voters will likely make these decisions according to their real feelings. They will cast votes against a candidate they dislike and they will vote for candidates they like. With balanced voting methods, voters can freely express dislike for particular candidates and that means they are not forced to resort to strategic methods to express this very real and very natural belief.
With IRV, Celeb voters are likely to put the candidate they favor in first place on their ballots. Ghost will garner at most 12% of the vote, so Ghost will be eliminated in the first round of counting. Now the Ghost voters may all decide to not even list a second choice since that would mean voting for a candidate they dislike. The choice between the two Celeb candidates lies in the hands of these Ghost voters who do not like either of them. If just a little more than 2% more voters (necessarily these would be Ghost voters) list Beth Celeb as a second choice than those who list Al Celeb as second choice then that would give the election to Beth Celeb rather than to Al Celeb. Under IRV, the Ghost supporters would be well advised to give some serious consideration to whom they consider the lesser of the two evils. As with other traditional systems, with IRV a little-known candidate does not stand a ghost of a chance and the only real choice is apt to be between two celebrities.
With IRBV, voters have more freedom of expression. Might any voters decide to cast their first priority against some candidate? Since there will be only two counts of the votes, some Celeb voters may well choose to cast their first-ranked choice as a vote against the Celeb they dislike. Presumably they would do that if they preferred Ghost to win rather than letting the wrong Celeb candidate winning. If enough voters choose to vote against one or the other of the Celeb candidates then Ghost actually could survive to the second round of voting and if a preference for Ghost by the voters whose Celeb candidate lost in the first round then it is quite possible for Ghost to become the winner. Under IRBV, this race is wide open with any of the three candidates having a chance to win.