Let me try to answer your questions
First, bluz DK doesn't have a USB port built in, and while it can talk serial, it would need a USB to Serial adapter. This isn't the intended use of bluz and it is really meant more for wireless communication.
Bluz connects automatically to the Particle cloud, the device ID and registration is already built in. It can connect to a smartphone and talk to it as well, but this would likely require your own app. Alternatively, you can use the apps we already have to talk to it.
Bluz can also support the Nordic UART protocol to talk to a smartphone, so that is available as well.
Getting data to a website is fairly easy, you can see some of our example projects that do just that:
Both take sensor data and send it directly to a website. People can even login to the website with their own Particle username/password and get their data. There is fantastic products support surrounding bluz and the entire Particle ecosystem, so this is pretty easy to do.
Let me know if that helps or if you have more questions.