the lenght is directly proportional with your height.
there are DRAGON/UNICORN/PHOENIX cores and each has its own special properties. Unicorn is the most pure and hardly accepts a master who wants to practice dark-arts magic. dragon is the most temperamental and determined. phoenix it's known for having a mind of its own because of its origins. The phoenix, the creature is one of the most intelligent and independent creatures. it's all on pottermore wands.
I received a azevinho, holly Phoenix Feather core wand (this was Harry's). It makes me a little nervous to be honest. My wand is 10 inches and reasonably supple. Add me! I just made my account, my username is EchoSilver20202 :)