I recently wrote a guide (https://blog.mapbox.com/styling-mapbox-terrain-rgb-c75...

I recently wrote a guide (https://blog.mapbox.com/styling-mapbox-terrain-rgb-c75d1cd71...) about extruding the contour lines within the Mapbox Terrain vector tiles (https://www.mapbox.com/vector-tiles/mapbox-terrain/#contour) that could be helpful to you as soon as I update it to match our recently re-released Studio product.

Check out https://www.mapbox.com/help/access-elevation-data/ for more background and let us know @Mapbox if you have questions!

Note - I work at Mapbox