I haven't flown EY since before the pandemic. If my experience is still good, the trick is to not go to preclearance when the lounge staff say you should, but later. When the screens say your flight is boarding, it is usually not boarding, what they mean is it is time to go through preclearance. By that point the whole area is fairly empty, assuming there are no US flights leaving later (most left at roughly the same time in my experience). Of course if you have GE it is even faster.