Mine was neutered at 3 years old - we are coming up on a year post neuter. I was also worried like you. In my experience the only thing that changed was he marked less in our yard. His behavior was still the same - which for me was a relief because I did not want a change. He's also a little less of a A hole if another dog is walking down the street - not sure if that's my training or the surgery.
Now, he is not a Sch dog - so I cannot comment on drives. If he were - I would be more worried about drives and neutering.
Because he was older it took him longer to heal. I would say day 3 post surgery was the most challenging and uncomfortable for him. But he healed nicely.