RE Unit width, 5 or 7 are the magic numbers in my opinion for elves/smaller unit bases.
5 wide is quite simply going for more ranks to get/negate steadfast and try for the max 3 'free' combat res. (each rank apart from the first gives +1 CR to a max of 3)
7 is taking a more combat approach, getting in more attacks then the enemie (often you'll have seven fighting 5) while still maintaining a few ranks for CR and more importantly seeking steadfast.
As to different weapons in a unit generating attacks, you have it right apart from illegal choices
For instant a unit of 4 Ogre Maneaters in 2x2 formation.
They have 3 attacks each (and being monstrous infantry they can make their full number of attacks in subsequent ranks)
The front 2 are armed with great weapons, and the rear two are armed with a brace of pistols (2 pistols, so +1 attack amongst pewpew goodness)
The unit would make 14 attacks (6 GW attacks and 8 pistol attacks).
