Beyond what has already been discussed:
EoTH - Being able to stack some (as in 3+) Ascendancy/Syndic/Phalanx capital ships on one plane, 4+ Chafs (power to weapons has a minimal shield drain compared to Victory-class ships) on another plane, and 6 Vigilance Gunships all in a tight bunch in a line formation is a beautiful way to melt incoming opponents. I'll generally put a leader and an Interdictor behind the line. I like to use Baron Fel and all the starting fighters as a defense force at Nirauan or Bilbringi (top priority target for me early) to free up capital ships for use elsewhere. The only thing I really do later is upgrade to Phalanx destroyers once they become available.
NR - I find the starfighter advantage to be somewhat muted except against capital ships until E-Wings become available. Corvettes are, for my money, the best anti-fighter ship option in the game, though. I never hyperspace out without them. Era 5 is awesome, when the Mon Cal Cruiser with Assault Frigates and/or Dreadnaughts combo gets fully upgraded to Nebulas with Bothan Assault Cruisers.
IR - If you reach Era 4, you've failed. TIE Defenders are so superior to any other fighter in the game that I get bored with using them beyond the emergency "going against an SSD with 2 HVGs supporting" battle against the Pentastar Alignment. ISD-2s, VSD-2s, and Lancers are my fleet composition of choice, but the ISDs are annoying compared to my EotH and NR fleets due to the huge battle map space that the ISDs take up beyond their visual representations. It makes formation maneuvers difficult.
Not sure whether you mean positioning/tactics on the galactic map, or just within space battle mode, so I'm leaving that alone.