Many of the values can be written in as Meters.
In general GAEA is agnostic.
Your terrain definition on the build tab can also be set that way.
This represents a volume "workspace" better representative of how we perceive scale as a 3D cube/rectangle
So what you could try is say set your perceived scale and height to 1000 , 1000. If you wanted te mountain t be 500m heigh. You could then set it capped using various nodes, like height and type 500m
Once you export mind, your dimensions would still need to follow your original scale ratio, especially if normalising data.