Pads can be set up either way, Samanthia, and you can even open a pad without any account at all, they just expire much faster if there's no attached account. You have a month with no activity without an account, 12 months without activity if you have one. If you have an account, you can make every pad you set up private or public however you like, and you can make the link whatever you'd like, instead of the autogenerated random ones that non-users default to.
Nashoba, a single account isn't one pad, it can have literally a dozen pads open if you want it to. Having an account gives you a new base url, but there are still multiple sublinks. I know with Koku, the pad was always "thevault.titanpad.com/_____", and so far as I know all of the pad systems work that way.