Hi I'm Mirak.
About Mob Captain Spawn, how do i set the spawn distance so they don't spawn underground but on the surface?
1 more, how to manage their number to spawn?

That's all, thankyou!!

You can't yet determine how much they should spawn on the surface or in caves, that feature is planned.

To configure how many spawn, you can run /function ps-mob:config in chat.
In the menu you can then lower the cool down or increase the spawn change to increase how many MobCaptains spawn.