I don't think Miloh will change much. I know you haven't seen it but Kaji is still the crazy man he was before his neuter. He was neutered a little after his first birthday. He's still full of energy and spunk. He's just too scared to show off in front of you. He was a scaredy cat even before the neuter, so nothing changed there.
He will be uncomfortable at first, and it will take a while before all the testosterone is finally out of his system. It doesn't all just magically disappear after the neuter. It's more like it slowly flushes out of his system.