Suggests a single database so multiple emails can be sent to same prospect, but that's not clear to me. If such a database can be populated with jotfo

3. suggests a single database so multiple emails can be sent to same
prospect, but that's not clear to me. If such a database can be populated
with jotforms=good, but what is it adding? why not mail chimp alone?

Depending on the integration you are using you can use a set or custom email database which receives the information. We don't just use mailchimp as there are many differences and requests for preferences among various emailing systems that some users prefer over others which is why.