How to control the size of text so they look pleasantly for readers?

Here is a solution for map object:

charsize = cgdefcharsize()

main title: charsize * 1.0 cgmap_grid: charsize * 0.7 longitude: charsize * 0.6 latitude: charsize * 0.6 colorbar title: charsize * 0.7 colorbar label: charsize * 0.8

To illustrate:

Figure 2

Later I will provide other examples for other type of plots.