HubSpot Admin Questions: Removing Superadmin & Email Validation Tools

Our old Head of Marketing just left and I was assigned with updating our HubSpot. I wanted to ask if anyone has experience with removing a Superadmin: Can they be removed entirely without any expected issues? Are there any permissions I should be mindful off to not cause any problems later?

Do you have a preference for the best tool on the Hubspot Marketplace for email validation? Debating between DeBounce and Clearout.