So with most maps that show significant distances and have stylised depictions you wouldn't want to show one mountain for every mountain in there... because there will be many many thousands in a mountain range.... way more than you could hope to depict and remain even slightly coherent with this style (as a general rule the only maps that are essentially showing 1:1 mountains in a range are generally ones that look "wrinkly" or more satellite-style)

So basically all you need to include to give people looking at your map a sense of scale is a scale bar of some sort. You can use just a simple scale bar (even just one that shows what 50 miles looks like, for example), a border scale, a labeled grid over the map, basically anything that someone can look at and say, "oh, it's about this distance between here and here"

In the absence of a scale like that the only cue that someone could use would be things such as relative size of settlements or objects of other known sizes for a clue... but if you put your scale in explicitly then you can be as stylised in your depictions as you want and people will still be able to figure out how far apart everything is. That's all that is meant by scale when it comes to practical mapping, some indication of how far apart the things depicted are... while this can be done by showing some things at actual size it's much easier to just include a scale bar of some sort.

(Fun Note: a scale on maps doesn't even have to be a formal measurement... a dotted line between one place and another labeled "50 paces" on a treasure map also counts as a scale)