Marketing is used for the campaigns and has dependency on DSM(Decision Strategy Manager). So you have to learn basics of DSM and Marketing concepts. So would suggest you to stick to CSSA and then you can learn Marketing concepts, then the concepts will be easy to understand/implement.
As a Marketing developer you are expected to customize or create Marketing related rules(segments, offer flows, campaigns etc) along with PRPC rules.
Pega Marketing is a strategic Pega CRM application that relies on Pega 7 platform.
If you work on a Pega Marketing project, take the Pega Marketing Consultant course. This knowledge is necessary for both system architects and marketing consultants. For this course, you do not have to be a Certified System Architect (CSA).
If you will be a system architect in the project, follow the system architect track as well.