Without a more concrete example of the kind of question you'd like to ask, the answer to your question here is: It depends.
As for WordPress Development vs. Stack Overflow, that also depends. There is likely to be a bit of overlap in each of the sites. Read the Help Center. If it's still not clear to you, you can always ask on the respective Meta site or in chat (with enough reputation to do so).
If nothing else, take the Tour and read the Help Center so you get a better sense of what is, and especially what isn't, on-topic for the site.
One thing for sure: Web programming questions are off-topic here on Web Applications.