As with most puppies, you are going to be entering a big roller coaster ride! At least, I did! I kept on top of my training with Angel, but there were so many times that I felt like I was talking to a wall! And now at age 2 he is turning into quite the little guy!
But on castration, he was done at eight months old. He had one testicle that did not descend. My vet told me to do it sooner than later. No regrets. As far as calming him down, no not really, not for him. But I do believe for some it does calm them down.
I don't think it will interfere with training him.