Card counting is definitely not a myth. There are different versions. The movie “21” is based on a true story. Now while it wasn’t true card counting, it was theory based on probability. Once the +1 or -1 count got to a certain level (I believe it was +8 or -8), then the theory was that you would have a better chance at guessing what the next card would be, therefore upping your chances of guessing correctly and hitting or staying at the right time. If you have a quick mind and can count by 1, then this is a usable strategy and you can work it alone. The movie is purely Hollywood, but the premise behind the movie is true.
As for knowing how many jacks or queens are left in the deck, that is much more difficult and to be honest, I don’t know of anyone that good to accomplish that feat.