The reason the 90,000 soccer stadium doesn't take time is that they have hundreds of security staff that is getting people through. A 900 person broadway show has only 2-3 people checking. The soccer game also has several hours to get everybody in, whereas the broadway show only has like 30 minutes. Those two things combined is why the soccer game speeds through people quickly whereas the broadway show is slow.
When the NFL used to do pat downs at the stadiums, male security guards only patted down male patrons, and female security guards only patted down female patrons. That is still the case for those guests that can't go through a metal detector due to a pace maker or the like. So if a story occurred where a male security guard at Disney groped a teenage girl in a pat down, well that idiot deserves to be fired for breaking protocol.
How much metal detection slows down guests will depend on how much security Disney uses. If they use the same amount, it's going to be ugly. If they at least double if not triple security, they should be fine. Perhaps a slight slow down but nothing too bad. Where to place that additional security to fit at some of those entrances and bag checks, that's an interesting question.