How do you mitigate a German Shepherd's chance to be reactive over 20 months, prior neuter?

A challenge on the way will be to protect my German Shepherd from all dogs reacting to being not neutered. A lot of dogs even friendly ones may react to unaltered males. A fight can make my German Shepherd be reactive to all other dogs for life, my goal is to prevent this and have no dog fights. My breeder's contract signed requires my dog to be 20-26 months to get neutered. I'm going to talk to breeder and vet, about 15 months potentially. My vet has done German Shepherds at 6 months, and those dogs have been fine. But I'm concerned my dog will get hip dysplasia if neutered early, I'm also concerned sh*t happens along the way and my dog ends up aggressive because someone's dog decided to attack and make my dog reactive.

I struggled with this. I neutered my GS at 15 months. I did an X-ray on him to see how his growth plates were doing. At that time they were closed. Before he reached the 15 months, I got involved with a well balanced trainer. By that I mean, one that believes in positive reinforcement but is also not afraid of chain collars and e-collars. These are very opinionated breeds and we need all the tools. The trainer did 1 on 1 classes as well as group classes and town outings. The group outings and town outings did wonders for my GS. He does not react to any human or dog anymore unless provoked