The TYP file is only needed to change from Garmin defaults. The contours are types x20, x21 and x22 (minor, intermediate and major).
By adding entries to the TYP file you can override the default display.
There is no way to flex this according to altitude with an existing map. To do that, the map would need to have been compiled with different line types - such as 'minor contour over 5000 feet'. Possible in theory but impracticable unless you have the source data or can write code to decompile the map and have the rights to do it.