The selection very much depends on the time of year and the people who are at the show Elliot. There are fewer for adoption in the winter months. All hamsters that will be on the sales bench at a show will be booked in the week before. They will come with a pedigree and you could ask the person who is dealing with the sales who bred the hamster you chose and then you could have a chat with them if they are around.
They will certainly be tamer, probably larger than a pet shop hamster and you will know their history.
Exhibitors don't breed to sell them at shows - the simply use the shows to rehome babies they are not keeping themselves. You never know what will be available till you get there and look really and if you want the best choice then arrive nice and early