It's great that you are socializing him so much!! Socialization alone will make him so much more comfortable with his surroundings, no matter where he goes.
Just like with people, some dogs like each other and some don't. Just because they are socialized doesn't mean that they will like all other dogs, but the socialization will make him more comfortable and confident. If he doesn't like another dog, don't force them to spend time together. Some dogs get along and some don't. Some become best buddies instantly and others take a while to warm up to other dogs. Your Yorkie will decide who he likes
All you can do is to expose him to as many experiences, places, people and animals as possible.