Hi Changch,
I wouldn’t totally disregard customer journey mapping! It’s true that I haven’t used it in my current position, but I do think a lot of people find value there and that many companies do more in-depth worth there.
And I can really only speak to the research courses that I took, so I’m not sure what your best options may be! I would take a look through the options available at whichever location you are considering and would probably select a mix of them for a generalized certification. If you click into all of the different courses, there’s a lot of helpful info and some are just going to make more sense in terms of your interests or job. Sorry I don’t have more to say here!