On the topic of cat personalities, I used to have a really shy and slightly big cat.
She would scatter away at anything too loud, but she didn't have a problem with my little sister who is loud most of the time. She doesn't hiss or do anything crazy but she just scatters away and hides.
We later got another younger cat, and she was quite the sweet heart, sometimes her attention giving toward us got annoying, but she was sweet nonetheless.
However, the longer that younger cat was there, the less shy the older one got, the older one got more brave and would stay out in the living room more (She would still get scared stuffless at the slightest loud noise, however.)
It's weird how cat/dog personalities work, I guess they're just less instinctual than their ancestors.