There are two primary ways to markup your pages with structured data to help Google power your rich cards / rich snippets. The best way is to use on-page code markup, schema, to markup your pages as we discussed yesterday. But you can also use the data highlighter tool, which is more of a non-coder way to do the markup.
I asked John Mueller of Google which trumps the other. So if you use both the data highlighter on page A and page A also has conflicting on-page code markup, which will Google select.
John Mueller said they are "pretty much equivalent"." He said on Twitter it is the same thing has having conflicting on-page markup, Google will have to pick one or ignore both. "Like with other sources of structured data, they should be consistent with each other if both are used," John added.
Here is the tweet:
They're pretty much equivalent; like with other sources of structured data, they should be consistent with each other if both are used.
— John ☆.o(≧▽≦)o.☆ (@JohnMu) August 18, 2017
So like with anything you do in life, be consistent - it is a rule I live by.
Forum discussion at Twitter.