The most important thing in map typography is readability.
Especially in maps there are a few problems with that, because of the background and the small space.
So if you have a font type which is located over mountains or other problematic structures you should choose very readable fonts.
Another good thing is to outline the font with a lighter color in order to maximize contrast between letters and background.
E.g. Black letters on a dark brown mountain could be outlined by a lighter brown to pop up the typeface.
Very nice is a light glow around the letters. It's easy to do in photoshop.
I'd say it isn't always the easiest task to find optimal readable fonts if you search for typefaces with style and
flavor for fantasy maps that aren't out of date.
It's part of the schooling in graphic design, to be at the pulse of fonts. There are websites for typography and fonts.
Key for choosing a special and yet fitting typeface is the association one has with the general form of it.
A hint could be the historic period in which fantasy plays. e.g. If it is a gothic world, choose medieval black scripts.
If it's SF, choose a technical looking typeface. If it's a desert map, choose egyptian looking fonts. etc.
In maps another thing is important. Typefaces for different things should be different, in order to communicate better.
The Typeface for mountains, cities and rivers should be different on the first sight. So that anyone reads something
on the map, he knows from the typeface, what it is. That is very good if there are many labels on small space.
If you want to fill big spaces with e few letters, the only way is to maximize the letter spacing. Sorry.
Do NOT stretch fonts!!! A designer works a year or so on a professional font family and develops it to look most
esthetically with a maximum of readability and a lot of more things. If you stretch a font, you destroy all that work.
I hope that helped a bit. If there are more questions about typography, please ask.