Please consider the following:
Adult cats will be fully vaccinated. A kitten will only have its 1st shot, and will need 2 more boosters in 4-6 weeks ($25-$30 ea.) A kitten will only have its first deworming, and will need 1 or more treatments ($10 ea.), plus fecal parasite checks ($13 ea.) Rather than declawing a kitten, we may have an adult that is already declawed, saving you the expense ($100) and the hassle, and saving a cat the trauma.
Kittens only stay small a very few months and as they mature their true personalities emerge. A cat is born with a certain personality, and it is what it is. There is no such thing as "molding a kitten's personality."
If you want a cat of a certain personality adopt an older teenager or an adult. This way, what you see is what you get. This is the cat that will be part of your family for the next 15-20 years - not the little kitten that was so cute!
Likewise, it is impossible to predict what a kitten will physically grow into as an adult. Blue-eyed kittens grow into green-eyed adults. Small kittens grow into jumbo cats or seemingly large kittens may turn out to be petite adults.
Kittens are very energetic and playful. They do not understand the difference between climbing up the wonderful cat tree that you bought for them or climbing up your expensive draperies or your pants leg - or even your bare leg!
They do not understand the difference between batting around their jingle ball or batting around your pearl earrings or batting your favorite vase off of the shelf. Kittens wrestle and play very aggressively, are easily stimulated and need constant attention. Kittens, especially when left alone, may destroy your furniture, your phone wires, your plants or your shoes. Adult cats are calmer and are not as likely to destroy your furnishings or keep you awake at night.
By far, the most common victims of animal bites and scratches are children. Kittens are still learning how rough to play and what it means for humans to have no fur.