Welcome to the group... I have a BMD who is 3.5 years old and had previously owned 2 other's. I also have 2 Leonbergers (soon to be 3 and 2). I understand what you are going through with the pulling on lead when meeting other dogs, but I think you will find the obedience class very helpful for this problem. When I'm brave enough to walk all 3 of mine at once, I find it is best for me to move off the path and make them sit when another dog approaches. This seems to calm them down and they get used to knowing that they don't get to greet every dog they see.
As for the being mouthy still, I have found the best thing to do is ignore them when they do this, as usually they are trying to get our attention. Once they stop and settle down, we pay attention to them again.
Enjoy your pup!