If you want to change your email or signature when creating a new campaign you don't have to change your user settings. You can also tailor you email signature for each campaign you set up.
You can choose the email and create the signature you want to use. The email and signature associated with your account are selected by default in the dedicated field.
Once the campaign is created, the automatic campaign emails will have the signature and email you defined previously.
🧐 Remember that once you saved your email and you signature in the settings of your workflow, they cannot be modified.