I don't have rats anymore but I used to keep them a few years back. They are lovely pets, you won't regret getting one
I had 2 males and a female and there wasn't a lot of difference in their temperament. The males were lazier so I suppose easier to handle but my female was so tame she'd sit on my shoulder whilst I walked around the house, I loved her to bits. I doubt it was related but she lived longer than the boys too.
Cagewise it depends on how often you are planning on letting it out. Mine weren't in huge cages but they were out for a vast majority of the day so they didn't need huge living space as they mainly were there to eat and sleep. If you aren't planning on letting it out loads though a bigger cage would be more ideal