That isn’t possible with FoxGuard (at least, not yet). However, the plugin ProtectionPerms will probably do what you want. There isn’t any fine-grained mob spawning control in FoxGuard either, and I’m scratching to think of a Sponge plugin that can handle that intelligently. I’m not sure what the capabilities are of @TrenTech’s recent MobLimit plugin.
Protecting the whole world is easy however - just make a handler (basic or group) that prevents block place and block break for the default group, and link it to the world global region. Check the FoxGuard Wiki for more info.