I can’t answer your questions specifically because I don’t know the Campaigns module well enough, but I would also recommend sticking with SuiteCRM and nothing else, if that is possible.
I personally played with Mautic integrating with SuiteCRM, but then I realized that a CRM tool with Campaigns shouldn’t need any 3rd party tool to send emails. There’s a good chance that everything you need is already there.
You might need to add some functionality with code, but please do and then give it back to the community. The effort you put into that is probably similar to the effort it would take to integrate with some 3rd party tool.