You don’t <i>have</i> to use the connect computer wizard, you can simply put the workstation on the domain – but what the wizard can do is import a local user profile to the domain user and set a few permissions for you; like giving the user remote access permissions and linking that workstation as their default machine.
Anyhow, to answer your question: No this will not block the computer/laptop from being used outside of the domain and yes he would still be able to use the laptop without providing domain credentials. He would log on to the laptop as a local user, which you would need to setup on the laptop.
In Windows when you log on to a domain, it actually caches the domain credentials used to log in. So your user could in fact log in using his work account, even when at home, and if you are not using roaming profiles he will have all the same settings as he does when logged in to the domain. Obviously server shares etc. wouldn’t be available unless you set up a VPN.