Do overhaul mods change or add elements to already existing leveled lists in Oblivion, or do they add their own stuff to custom leveled lists? I ask because I am not sure if I still need to make compatibility patches for the mod I am making (Oblivion Prelude: Kvatch).

For example: if I use an existing creature leveled list to spawn enemies in a dungeon, will that same list automatically produce creatures that come from the overhaul mod (like MMM) if it was installed?

Overhauls do add their own content to leveled list and may edit leveled lists as well, but the bashed patch can take care of many compatibility problems for those. You just need to make sure your mod is http://wryemusings.com/Wrye%20Bash.html#LeveledLists. If your mod just adds content, put instructions in your ReadMe to have the relevant plugin manually added to the Leveled Lists list of Bashed Patch, plugins that only add content are not added automatically.

Thanks for the reply. But what if my mod does not alter any leveled list at all? Do I still need to tag the plugin?

No. If you want to see what type of compatibility patches you might need, look at Kvatch Rebuilt. I think the bigger concern might be NPC AI packages, maybe a script or two as well.

Edit: wording

Ok, thanks for the advice. I'll take a look at KR when I have the chance.