We know Nick became a Grimm somewhat late in life or not good question. As Kelly said women became Grimm's at a younger age, that somewhat was off for Kelly because we think he was a Grimm but 20 or 21, should we add the being half hexen made the difference.
In the books their no other Grimm's noted that were police officers. We also know that to learn to be a Grimm, Nick guide was a wessen Monroe, also not the likely way to be trained as a Grimm.
With these ideas how does that change thing or does it?
Probably does change things. The story goes that Aunt Marie never told Nick of his heritage until she was near death and that also seems to go against type. For all of his life Nick lived as a kehrsiete until his early thirties. After that, he was breaking out with Grimm background information and Grimm lore supplied by his mom, aunt and best pal. What an indoctrination.
And a slew of wesen coming at him all the while. Given the conditions of his new life, I'd say he made the transition well. He concerned himself with criminal wesen for almost all of his career as a Grimm. He was very flexible in his acceptance of most wesen, even if he did not respond well to Juliette's change. I never felt as if he were a bully in any sense. And although his wasn't a perfect record of wise judgement, I believe he handled most of his encounters with the unusually strong and vicious types intent on killing him with a response equal to the situations. The one exception that comes to mind is his killing Kenneth and I was glad to see it. There were too many instances in which he showed compassion to wesen to deny it was a part of his Grimmness.
I enjoyed his instinctive affiliation to many wesen; imo, he was more than willing to live in peace with his wesen countrymen. It gave the show a balance that spoke of Nick's openness to everyone on a person to person basis - free of prejudgment. The exact same thing can be said of all the major characters on this show; and we as fans got to see the camaraderie that diversity can bring.
No matter how Nick would have started out his life as a Grimm, for me the character was the new Grimm, one who truly did bridge a gap between what were historically hostile groups, and Monroe, more that anyone else, began that journey with him.