Slitherine

Nothing in the manual (yet again another poor manual).

What are the pros and con of the various fight formations?

Having tried all the formations, I don't think there is any benefit. All the formations are just way too spread out (especially late-game when fighter swarms are 1000+ strong) to be useful, and fighters tend to be much less responsive than they are when allowed to scatter. I don't think there is any purpose to formations other than looking cool.