Title pretty much says it all. I don't make mods but was wondering if this was possible. I'd love to be able to see the names of rivers, mountain ranges, etc., as well as border lines on realistic maps. I've never seen it in any of the mods I've dled.

The answer is yes. Go into the WB and look at the "Landmark" function.

Can you change the landmarks look?
Maybe if they were just black letters they would look better.

Alt+S lets you do it without opening the world builder. I use it to label rivers and things.