Of course you can edit/re-edit your character once creating it. If you see something that's a bit off, merely go back to the Log-in screen and log in. Once your characters are loaded up, there should be a button below your character that says 'Edit'. Then just click on it and edit away. Pretty simple.
When it comes what breed you'd like to lurk around on, there really is no pros and cons for every individual's views of the canine and feline models are different so it's up to you. You can linger around on both if you like for you can have more than one character.
Hope my poor explanation helped ye' at least a little.
If you have any further questions or need something to be made a bit more clear, don't hesitate to ask.