Changing fonts and styles with notes master

I changed the style for the font size in the Notes Master from 18 to 12. Now the font size has changed on many notes, but not all.

I am not very familiar with Impress, but should I assume that the font that did not change was directly formatted? (Someone else created this and who knows what they did.)

If so, is there a way to remove the direct formatting from all of the notes at once or must that be done slide by slide?

Some related questions:

Is there a difference between changing the font in the notes master with direct formatting as opposed to changing it with styles? That is, would the effect be the same?
When I open the notes master, what seem to be slide masters appear on the left side of the screen. Is the notes master associated with all of them?

Would appreciate any insights.