Personally I prefer to play with whatever the default settings whatever they are and
tiny/small/med galaxy
9 intelligent opponents with unknown junk
my civ is either all production or all econ with full morale boost.
Now all you have to do is ignore everyone colonize many worlds, research planet takeover pic a specific weapon get a bit of speed and logistics and easy victory...
I mean, get a fleet of whatever and abuse your speed and take your first strike. if needed for the beggining get starbase with military assist. have 1 to wahtever ship building planets and the enemy cant stop you. DESPITE the comp having insane research and technology. Aside from playing annoying huge maps where management is nigh-impossible.
Maybe this is just 1 way of playing, i'm hearing from others they are winning with trade etc etc. I never build a single trade vessel nor is trading tech required they just fight amongst themselves and i pick them off one by one. if others declare war on me take their fleets and eventually their planets, their measy movement speed of 2 cant reach my 3-5 movement. Managing the econ is lots of work too. tax up to approve greater than 65%and specialize in whatever you need.
BIGGEST BIGGEST problem (maybe not but possibly) Try this, this is my aultimate mid-endgame say you have all 1 class (Medium ships with a couple of fleets ~ 15ships)
"OOO! super duper new weapon tech!" (ex Ripper) Make new ship, junk it up with rippers and a few warp engines and upgrade ALL your ships for 200000000 credits.... poof debt goes to 2000 and you get super ships.... same goes if you buy hero buildings. its great but isnt it cheap? maybe a oversight? i mean should be some sort of disadvantage of doing this.
Otherwise great game... albiet tad easy, but thats why its fun!