Having played imperial's extensively and chaos more recently, I can tell you this, my holy crusading friend: when you are playing imperials, you are a shit ton more clustered. Your ships have lots of battery/lance AC/torpedo synergy and benefit from staying close due to both that and your short range. You can extend a bit, more like a curtain or more line like, depending on situation/your fleet/his fleet/preference, but unless you are playing against eldar your ships should almost never stray far from the pack.
When you play chaos you have somewhat more leeway, but your ships, despite the stronger attack value over the imperial equivalents, will die surprisingly fast if left unasisted. Due to the faster movement and longer range of chaotic ship guns, you can do things like pincers and flank strikes...but your ships will ideally always be within single move/shoot of each other, MAXIMUM. You would have to ask horizon for more info about using chaos escorts, I believe he has quite a few in his fleet. Infidels, if I recall?
