First, there is no official "teacup" poodle. There are TOY poodles. And those are poodles that mature under 10 inchs at the shoulder. "Teacups" are runty dogs bred back agian to produce more runty dogs. They usually have major leg issues, can have heart, teeth, and eye issues.
A good healthy toy poodle(watch for knee issues in the parents) is a joy, easy to train, happy without being hyper, etc. They need regular grooming, and brushing in between. Every 6 weeks is a minimum.
I treated my toy poodles like big dogs, expected the same behaviors and they were a absolute joy to have. They'll do agilty and obediance with the best of them. Just don't treat them like a baby frufru puppy-wuppy, and they will be a grand dog.
I'd go to your local branch of the AKC breed club, and see what they tell you. A poor breeder will give you a dog that will cost you thousands of dollars and you'll get a dog that has major issues. Ask to see the parents and look at their back legs. If they bow outwardly when they walk, then pass on a puppy. If the dogs have buggy eyes with tiny muzzles, pass on a puppy. Poor coats, or dogs that "hop like a bunny" or run with 3 legs, pass.
I hope this helped. I do like poodles, as they can be the most intelligent happy dogs there are.