For the settings, "true" means the content is enabled and "false" means it is disabled. "brutalcontent" allows explicit npc executions. "messycontent" appears not to be implemented yet.
The game comes with a modding guide in the "Mods" menu, just click the "Help" button, but there is no guide for mods compatible with Aric's mod. The main reason is that this mod is not designed with the intent of being compatible with other mods and Strive's mod system has limited ability for mods to coexist. Also, this mod is currently in active development so any mods made to work with this could become outdated within a week or two. If you wish to add content as part of this mod, it's easiest to simply join the development on Discord, link in the first post.