When sketching wireframes on paper, we normally use lines to indicate text. How do you indicate visual weight for different text sizes, though?
Since there is no actual text in your sketches I think it is not that important to communicate the text sizes on your wireframe.
The only thing you could communicate is, that there is some kind of structure or different weights to text elements. You can do this by using different pen sizes or different colors (e.g. black and gray).
If your goal is to test text sizes and text structures a paper wireframe is probably not sufficient.
If it's only regarding text, it's part of the style correction for which there is already a standardized international code. Wikipedia.
In particular, these are placed in the margin with the underlined text:
- 12/14 = Size (always goes with line spacing)
- ROM = regular
- BF = Bold