I got Toki when she was 10 weeks old and I got Teddy when he was around 10 months old and they were two completely different experiences!
I do look back at pictures of Toki's puppy stage and remember how cute, playful, and silly she was (she still is!). But there are just some things that I don't miss (like having to wake up a couple times throughout the night/wee hours of the morning to take her out for potty breaks, the teething stage, having to keep an eye on her etc). It was fine at the time because I was home a majority of the day and she was almost never alone for more than an hour or two. I think I would have been really stressed out with training her and making sure that she wasn't left by herself if I had a lot of things going on in my life at the time like I do now with working and nursing school.
Teddy was already housebroken when we got him and although we spent time getting him transitioned and adjusted to our household, it was a relatively smooth process and not as intensive as bringing a young puppy home. If I were to get another dog for myself, I'd definitely lean toward an older puppy or adult. My parents took in a 5 year old yorkie and she was the best family pet!
I can't offer any experiences with Yorkies vs Havanese but hopefully someone else can chime in
