I must be looking in the wrong place data/English/Corestamps only has generic and chasms files..though they dont seem to contain any of the information I am looking for.
Heavenfall is doing he's best, there is honestly noone on the forum who knows the percentage of chance for mountains anywhere, all he says is the basic ideas of information can be found there in those files.
I speak broadly when I say "WE" have no clue what map you would prefer, even if you just say the least mountains, Heavenfall did give 2 map types to try out because they might be the ones, come on and be happy 
I'm not looking for a mod..I want a description of the map types with %chance of terrian, water and mountains
Just want to defend myself and say I only tried to assist you with looking by giving the link, I figured you wasn't too much into a mod.
I do think a mod is the best solution though, if nothing else you COULD create 10 new stamps without mountains that is fairly open, this will make sure there is less chance for mountains to appear on your maps.
Sincerely
~ Kongdej