mhm, does the distinction between red/black and pink denote these differences? Or is pink purely the evil areas. It's just that exporting the map via legends shows that the black/red areas are also evil.
You could backup your save and do quick embarks to see what they are like. There are 4 colours used for evil forest, marsh, etc. as far as I have noticed - two shades of purple, dark red and dark grey. Perhaps the grey ones are likelier to have dead plantlife, perhaps not.
Evil areas are generally pretty varied though. Plants (shrubs, trees and grasses) and undeads seem to be entirely optional. Only the vermin and various evil critters seem to be constant. In my experience, you are likely to find skeletons or zombies if the plants are dead as well, and unlikely if they aren't. The savagery doesn't seem to have any effect on this, as I have embarked into terrifying jungles which were just normal tropical broadleaf forests with few stranglers, blendecs and phantom spiders (ie. not even glumprongs or silver barbs).
Be warned that the wormy tendril grasses can be pretty annoying, as they twitch around with high frequency. Though I have to admit that evil forests with live trees, both evil grasses and the littered spider webs
do look very funky in pshycedelic way.