I have a dog who's massively loud and reactive when he meets a new dog. I mean barkbarkbarkleapleapleapbarkbarkbark. It looks for all the world like terrible aggression.
But this is only for about 30 seconds, and then he gets to being "let's me and you chase butterflies, yeah? After we've sniffed each other's bums, obv". I know what you're thinking; my dog is a bell-end. And he is 
So I'm pretty comfy with him around other dogs as long as I've got control of that first 30 seconds. After all, he spends weekdays living the high life at doggy day care, and we never get a bad report about him there (and they're pretty hot on bad behaviour, as they have to be).
One thing we do to mitigate this is to give him something else to do - it seems to be the case that if we can dilute his focus on the other dog, then he approaches things in a much calmer, more measured way. So we make him sit and wait for a treat, or wave a ball at him, or something.
Also, a dog trainer we know told us that the lead is like an electrical connection between you and the dog, but for emotions - so if you're relaxed, your dog is more likely to be relaxed.