AmigaFax can use all the standard Amiga fonts. Under AmigaDOS2.0 the ability to perform font-scaling means that you can generate quite impressive documents very easily.
The AmigaFax distribution also includes a selection of larger sized fonts from the Computer Modern series, which again allows very high quality faxes to be produced. These were generated from standard TEXfonts using the TEXF program. Note that these fonts do not contain the umlaut characters commonly used in Europe.
These include the fonts cmr10, cmbx10, cmssbx10 and cmtt10 in sizes from 29 to 103.
I would suggest that anyone using AmigaDOS 2.0 use the standard Amiga fonts. Even Topaz scaled to 30 point size or greater comes out quite effectively. Play around until you find a setup you like.