Typically notifications are ID from which site they are coming from.
But if you want to separate them, you could invite yourself as an admin with a different email. However you will still get notifications at the email that “owns” the sites.
For example, you get a free email from Google, call it siteAsales@gmail.com for Site A, and siteBsales@gmail.com for Site B. Add each to their respective site and then tailor your notifications settings for your primary owner email.