Can I set my content publishing status to "Unpublish" by default?

Yes, you can configure the default content publishing status using constants.
Set DEFAULT_OPEN_TYPE to close.

Accessing the screen

In the left sidebar menu, select [Environment] -> [Constants]. Then, click [Add] in the upper right corner.

Constant value

Enter the following:

• Name: DEFAULT_OPEN_TYPE
• Value: close

Click [Add] to save the constant. Now the default publishing status for new contents will be "Unpublished".