No, the -now just executes it faster. LIke, instant. It’s a bit like the windows command which seems to do the same.
The only thing you need to realize is, the user which executes the sudo command has to have the rights to do so. In the sudoers file you can actually set the user under which the server runs to allow for single commands to be executed on a higher privilege level.
Linux is very used to handle the principle of “least privilege”. You can read more about the sudoers file here: http://www.atrixnet.com/allow-an-unprivileged-user-to-run-a-certain-command-with-sudo/
It’s all a matter of security. You don’t want to be hacked on the regular account and have it be able to sudo everything. Like rm -rf * / (DO NOT RUN THIS!!!) which will remove everything from your file system.
As to the process.exec, I’d recommend using a script to first cleanly shutdown the Blynk server and after that shtudown the Pi. That way everything shuts down nice. There are several nice shutdown scripts for the Blynk server on the Pi to be found on the forum here