Truly secure and confident dogs don't feel the need to put other dogs in their place. the other dogs KNOW. I had a dog who, at a glance, appeared to let my girls walk all over him....but if they went too far he'd shoot them a VERY subtle look and they'd both turn into puppies, apologizing. He was a very interesting dog, very comfortable in his own skin. To be honest he didn't really like most people outside our family, he just "tolerated" them. Did not seek or appreciate pats or affection from strangers. I did notice that some other dogs would target him and try to get after him....and he didn't really care! We called him "The Lion King" and that's pretty much how he saw himself.
and yet someone else commented that as his confidence grows, so will his aggression...
Kaiser is a VERY sociable dog with people, very goofy and affectionate, and is an absolute gem with some dogs. I think there is something else going on here, aside from the idea that he's not confident. For example, if he was acting out of insecurity or lack of confidence, then why would he do it only to some dogs and not all? Why was it ONLY with aggressive males at first, and now also some females (again, not all, in either scenario)?
I don't think it's dominant behavior (as DunRingill has already addressed). I have what we think is a Finnish Lapphund mix... small herding breed with some very similiar behaviors to shepherds. He is very easily stimulated by other dogs and does similiar behaviors as what you posted. He will bite a dog if he gets close to them but it's not fear or dominance it's more like he is checking on HIS place and seeing what the other dog will allow him to get away with.
We have had a lot of success working with him on a head collar (Infinity lead or Halti) and counter conditioning using space because he wants
to be near the other dogs so his correction is getting further away and reward is getting closer and some food. He can now walk next to another dog calmly and ignore them but he can't be still within striking distance of them or he will bite. He isn't biting to break skin either (he's done it to my Kaiser) and likes to tease my dogs when he walks by their crates.
We don't use physical corrections on him because he has and will redirect on people. It's actually how we found out he had issues with dogs. I was walking him out of the kennel he was in one day and as we passed a dog, he bit into my thigh. I have no doubts he would redirect with a correction since he will do it without one. Since our relationship has built, he won't dream of biting me. When he got into a fight with one of my dogs last week, he turned mouth open when I grabbed him and I simply said "don't even think about it" and he stopped immediately.
Completely agree with the above and feel very lucky that my Kaiser is a lot like this is so many ways. He lets the girls in my house think they run the show but will calmly let them know when they've gone too far. He has amazing communication skills with other dogs and knows how to put reactive dogs at ease and ignores rude dogs to let them know their behavior is inappropriate and if they push too far gives very appropriate corrections without using his mouth most of the time. Love it about him. He's a little more social with people though.
Also, ultimately Kaiser loves to play, but this isn't an issue with him reacting because he WANTS to get closer. Once he realizes the dogs are "ok" he settles down and is fine to play. The initial reaction (scenario one) is seems full of fluff...like a rooster strutting around showing everyone how "great" it is. Also, Kaiser does NOT ignore rude dogs like Dakota does. In fact, a rude dog with behavior such as humping or stealing toys out of his mouth, etc, will set him off...except for the boston terrier he loves.