There are 4 templates you have to edit for each style...
forumhome_forumbit_level1_post
forumhome_forumbit_level1_nopost
forumhome_forumbit_level2_post
forumhome_forumbit_level2_nopost
In each make this edit:
Find:
Code:
<if condition="$show['subforums']">
Replace With:
Code:
<if condition="$show['subforums'] AND $forum[forumid] != X">
Replace X with the forumid of the parent forum from which you don't want to show subforums on forumhome.