Hello and welcome. It's nice to see someone who sets out to do her homework before deciding on a breed.
I have two Yorkie girls and words can't come close to describing how much I love them and how much they really mean to me.
I'm sure that people with other breeds can say the same about their fur-kids.
You should think about what size, how long of hair, is it ok if they shed, are they easy to train, are they high maintenance and so on.
I was on two Yorkie Rescues for years and fostered many a Yorkie. This was my final observation........they were all different, they each had their own unique personalities, idiosyncrasys, likes, dislikes and social behaviors.
The common factors to each one is how wonderful they are able to adjust to new situations, homes and families. I also could tell which one was socialized as a puppy and which ones were not. Some loved to play with toys and some would rather observe. I never had a yapper even though I know most small dogs can be that way unless trained when they first start exibiting that trait.
In the long run, you just need to socialize what ever breed you decide on. Take your baby to puppy-play dates or start one at your house once a week. Take the puppy when it's about 4 months (after it gets a rabies shot) to puppy kindergarden for training, then advance classes. Take your puppy everywhere possible. Let kids of all ages play with and hold your puppy (with supervision) so it will get use to the different ways it will be held and played with. Show your puppy how to play with toys and the fun of doing so.
As for how long you should leave a puppy depends on it's age. A 12 week old puppy needs to eat 5 to 6 tiny meals a day, and should not be left alone at all. When the puppy is older, start with just an hour alone at first till it gets used to it, then very, very gradually increase the time alone, but I would never suggest leaving your puppy alone more than 4 hours at a time regardless of it's age.
Keeping a Yorkies hair cut short is fine, but the hair is what makes the breed.
Buy some training books, especially on whatever breed you decide on.