Welcome to YT.
Although some may disagree, I think the general concensus is "yes", Yorkies can be challenging to housetrain. If you aren't gone for very long periods, they are just as capable of going to the bathroom outside though. No need to use pee pads. I will say my seven-year-old goes to the bathroom in the house all the time.
She does know where she is supposed to go though.
Yorkie pups are fragile and I would still be mildly concerned about hypoglycemia at 12 weeks.