Dog barks only at some dogs

I adopted some kind of Aussie shepherd mix (1.5yo, neutered male, 80 pounds) about a month ago and he very inconsistently goes OFF on dogs when we’re on a walk, but only some dogs. A few points here:

1. He does not react much to dogs who bark at him from a balcony or fence

2. He lived with one or two other dogs with his old family and appeared to get along with them fine

3. He was kenneled with another dog while at the shelter and he also got along fine with that dog, as well as other shelter dogs during group playtimes. He was also not a huge barker at the shelter from what I saw and what I was told

4. There is no real rhyme or reason to which dogs set him off. He’s slightly more reactive towards dogs closer to his size, but he also goes off on some small dogs. Some dogs he only barks at if they bark first, other ones he sees and will almost immediately start growling and barking even if they are ignoring him

5. He’s played nicely without any growling or barking with at least two other dogs while he was still on a leash

6. He hates just about any dog that lives in my apartment complex. If he hears them passing by in the courtyard, he will rush over barking.

None of his barks seem like the angry, ears flattnes back, snarling type, and he will shut up and calm down after a few seconds and it passes, but he’s big and I don’t want him to scare people or get into the habit. Also it’s embarrassing as hell and sometimes I don’t have the means to cross the street or turn back where we came from.

Right now, I basically either cross the street or turn the opposite direction or get off the sidewalk to walk on the other side of parked cars while there is still a good distance and he’s usually fine once we do that. I’ve also tried to redirect his attention with a high value treat before he even starts barking, but he does not respond to food once he sees something on the street that his attention latches onto.

Any tips on what else I can do?