I don't pretend to have answers. Just some observations based on my earned experience.
I've had mixed dog sexes in the house for a long time. At the moment, three females and one male. At various times I've had two or three females with two or three males. And I've been told that two females are a problem or two males are a problem.
My experience is simply this, if I set zero tolerance rules for nose to nose stuff or dominance exhibitions, that they seldom act out. If my rules and boundaries are consistently reinforced they are followed. And the mutts seem happier and livelier.
If I allowed the current four mutts too much license in their interaction, I'd have a mess on my hands. And I want my rules followed when I'm not around. I figure that since there is no blood on the floor, the furniture is not overturned, stuff isn't chewed or otherwise destroyed, that they must be coexisting according to my rules.
At the very first hint of an issue I act. It can be a terse 'hey' or it can be a nudge with the drop-dead command 'NO.' The mutts have great freedom that could lead to issues but my every moment attitude is my rules are MY rules.
Vigilance is my obligation. It is especially so when a foster comes into the bunch. I expect all the dogs to interact without posturing or dominance. Playing is fine unless I even think a dog is getting a little too into the play, and then the 'hey' or an 'enough' seems to refocus all the dogs.
Younger dogs need a little more direct attention if they are acting out and testing the waters or if they are more timid and subordinate tending. I have never been fond of bullies of any kind, and certainly not in my dog bunch. So I work to minimize attitudes between mutts.
Dogs are dogs and dogs have moments but I am of the opinion that with the rules well reinforced, those moments are brief and don't rise to the level of conflict, more like 'I have a headache and leave me alone' moments.
I've had dogs that a raised voice gets their full attention and response to commands, and I've had dogs that you feel like snatching them bald headed, and both extremes have adapted to my rules and interact with each other without serious incidents. But it don't be get'n done that way over night. Every day consistent reinforcement of rules. Consistent reinforcement of the rules. Consistent reinforcement of the rules.
Two of my tests for good interaction has to do with dogs not going to another dog's food bowl, and a dog waiting until a toy is abandoned to claim it. I expect my mutts to demonstrate restraint and respect in re the other dogs, to put it in human terms.
The dogs own nothing. Their mats, toys, schedules, meals, constitutionals, whatever are on my terms. And their ears are up, tails are wagging, play and prey drives high, excitement abounding, yadda, yadda, yadda. And they even stay out of my wife's garden.
Another one of my useless epistles. I really type too fast.
Mike A.
"I wouldn't touch that dog, son. He don't take to pettin." Hondo, played by John Wayne