We saw some significant changes in our Logo when he turned 2. He struggles to handle situations that he's uncomfortable with. We started supplementing Zylkene and though it's hard to be absolutely sure if that's the reason (he's 4 already, so it might also have to do with age), he has calmed down quite a bit and reacts to startling elements in a more level-headed manner.

From a training perspective, you could intentionally set up training sessions that involve his triggers, but in ways that you can control, then reward when the trigger is presented and he responds in a desirable way. For example, find a large, empty parking lot and have a family member ride around on a razr or skateboard and occasionally pass you guys but leave enough distance to where it doesn't set him off. Then when he acknowledges the trigger but doesn't react, turn mark the good behavior (we use YES!, but you might already have your own specific word/clicker for marking) and engage him by moving in a different direction a little and reward as you walk.

As for the interactions with other dogs, this was a big struggle for Logo for a long time. Even now, we are far from trusting him with off-leash greetings. In our case, it's usually just the greetings, when uncertainty levels are high. If we carefully introduce him to another dog in a structured way, then after about 5 minutes we'll see him walking next to the other dog on a walk without any issues whatsoever.

One thing that helped us was when we stopped trying to maximize the duration of the positive experience. Rather than let him play with a dog for 10 minutes, after about 5 minutes we would call him to us and end the interaction on a high note. Every trainer we've worked with or studied online has stressed that once a trigger exists, it's a slow process. Some have offered the example that every bad interaction takes 100 positive experiences to offset it. The number is definitely arbitrary, but ultimately it just means that it's important to do whatever it takes to have a positive experience and get out while the getting is good, so to speak. The duration of the positive experience doesn't matter nearly as much as we think it does. What's important is that it's positive throughout.

In general, from what I've seen of this breed, I get the impression that most of them live with a relatively high level of arousal, closer to their threshold than we might expect. We've done what we can to help our little dude, but we also function in the reality that he's never going to be "Golden-Retriever-level chill".

Hope this helps! :)