I don't want to pretend to be some sort of authority on this simply because I raised a child as a single parent and I have ASD, but I will give my opinion. Every relationship is different and there are many other factors that are involved and perspectives unaccounted for when you only have one.
My son and me have a very good relationship. He will always go to me first before his NT mother. I think his mother gets too emotionally involved and turns those emotions into manipulations. He feels manipulated by her and says as much in plain language that leaves nothing open to interpretation. With me, he can be sure that I'm going to say what I mean and have his best interests in mind every time.
I do believe in an emotional distance between parents and children and by that I mean that I am not going to dump my problems on him at any time. Also, that he can do so to me without expecting me to over-react based on an emotional response. I'm not the type of parent to take his side every time he got in trouble. If he messed up I was the first to tell him. Apparently, as my father who was a principal of a high school, told me, parents sticking up for their kids was close to universal and the one thing that ensured troublemakers remained troublemakers.
He is 20 now, and we have a parent-child relationship. We are not friends, he has enough friends, that isn't my role.