Dominance issues are going to happen, castrated or not. My alpha is castrated, my second is castrated and my lowest on the totem pole is my intact male wolfhound. I don't believe in castration of male dogs, but that is just my personal opinion.
I also don't believe you can "create" an alpha dog. You may do everything first with them, but that does not make them alpha. It may make them your favorite, but it does not make the other dogs see them as alpha. Max is my largest and tallest dog. Since his head is usually the closest to me, he usually gets his treats, food, etc. first. He is my bottom of the pack, in terms of hierarchy. Dominance is 90% mental and 10% physical, in my opinion. Cody does not throw his weight around, growling, challenging, etc. In fact he has never bitten another dog in my house, other than to slam ChiChi a few times, just to teach her to leave him alone, when he doesn't want to play. Even then, there was not a mark on her. He used only enough force to put her on the floor and hold her, or to grab her paw, when she slapped him with it and hold it until she submitted.
As far as introducing a female dog, you need to make sure that the dog you get, fits. Every female is not going to fit into every all male pack. Every male is not going to NOT fit into every all male pack. When I got Jake, I already had Cody and Max and we had no issues with fighting or aggression. Prior to Jake, I had tried to introduce female dogs, as I thought that would be an easier addition. Wrong. Cody was fine with them, meeting outside or off property, but would not allow them into the house. It just wasn't happening. I know now that it was the dogs and not the sex, as ChiChi was readily accepted into the pack, from day one.
Kathy