How Old To Neuter a Male Dog:

When to Neuter a dog

I would neuter my dog thusly:

Adorable small breeds: Pretty much any time after 20 weeks.
Adorable medium breeds: 6-7 months unless they're showing male behaviors.
Large breed dogs who are supposed to have blocky heads and broad shoulders: As close to a year as possible WITHOUT SACRIFICING PEACEFULNESS FOR TESTOSTERONE AGGRESSION. My dog, Ajax had to be neutered early because he had started GROWLING at people before he was even 5 months old!!!
Large breed dogs who don't need blocky heads: 6-7 months unless they're showing male behaviors.

If a male dog starts being skittish, growly, snappy, crazy-eyed, fearful, or roamy and deaf-to-training- You should ACCELERATE plans to neuter and head off the influence of TESTOSTERONE.
And get the dog into a trainer's purview before the behaviors are ingrained.

Certain breeds like Cavaliers, Frenchies, Retrievers, most spaniels, are in the Neuter-at-6-7 months category.

I have a list of dog breeds that are notoriously skittish and fearful - if you avoided those breeds it probably wouldn't matter when you secured the neuter.