SendGrid? Customize form?

If I have my site set up to use SendGrid for transactional emails, will the emails from this plugin go through SendGrid too?

Also, is it possible to customize the form, for example, add a field like “how did you discover our site” in addition to name and email?

Your plugin might be what I’m looking for as I use another permission marketing service, so I just need to collect a list that I can export and import into that service.

Thanks!