PromoBar can be configured on each subsite separately when using the Wordpress Multisite installation. You can also apply the same settings to all subsites at once.
On the Network page, you can limit the ability to access or change plugin settings for each subsite. Just select the "Apply for all sites and use as default" option located in the "Apply network settings" field, and select the necessary values.
If you'd like to have Network settings displayed only when the plugin is activated, and use an option to change them at later stages, find the "Apply network settings" field and set the "As default" value there.
To make sure that the Network settings do not apply to subsite settings, select the "Not apply" in the "Apply network settings" field. Save changes when done.