I had a retriever/shepherd X. We had her from 6 weeks to her passing at 9.5 years.
Because she had to be adopted early (unhealthy mom and overfilled shelter could not keep puppies together any longer), she never got the benefit of getting socialized long enough with her litter mates. We tried to keep her socialized with other dogs, but it was never enough to catch up on those missed weeks with her siblings. As a result; past the puppy hood stage, she was not nice with other dogs. A lot like what you described. She also had not learned to inhibit biting properly, so even when she did want to play nicely with other dogs, her play bite was too hard and a fight would ensue. However, in time, she calmed down and it became more manageable.
We knew it was worse on a lead because she wanted to protect us. So having a strong recall was a savior. She did better off leash. We learned to recognize the signs that she was getting more aroused. We constantly watched her and called her back before she started scrapping around with another dog.
When she wasn't in a calm mind state to start, I simply learned to tell people to leash their dogs and stay away because mine wasn't friendly.
And we had to be extra vigilant when the kids were around because she wanted to protect them.