My TB loves to pop his shoulder as well, what I do to correct this is by putting pressure on his outside shoulder with my outside rein. Almost like you are doing a roll back.
You don't want to bend your horse to the inside - you want to make sure your horse is strait.
There are great exercises to help with this - you can do this at the walk. Then move into the trot when you are ready.
Act as though you are going to do a 20 meter circle, but in a square shape instead. When you come to the point of going from one side of the square to the other, ask for the turn with all your outside aids, and by putting the outside rein on your horses outside shoulder.
Remember - your outside leg doesn't prevent the horse from popping their shoulder, your outside rein does. Your reins ride the shoulders not the face.
Here is a vid of my TB and I doing this but going around ground poles instead. All outside aids.