Pairing without a mood board

The reliable pairing rule is contrast: a serif with a sans, a display face with a workhorse, high contrast with low. Two sans-serifs from the same era and the same width read as a mistake rather than a decision, because the eye registers the difference without being able to justify it.

Match x-height across the pair, or one face will look larger than the other at the same size, and you will spend the rest of the project applying corrective font-size values per component. Check the numerals too: lining versus old-style is the detail that quietly makes a table look wrong.

One face used well beats two used carelessly, and a variable font with a real weight range often removes the need for a second entirely. The system stack is also a legitimate choice for body text: it is free, it never flashes, and on a product interface almost nobody notices.