Let me share my story. Back when I had only galciv2 I often checked "randomize intelligence" which gave the races a little variation, instead of them all being equally powerful (which is boring)

So now with TA I did the same thing.... and since it's been a while I played I selected "Tough" for difficulty, which should overall get races with "Intelligent" Settings (for reference https://www.galciv.wikia.com/wiki/Difficulty_level )

I carefully chose my custom abilities, started a few games, selected a good start with enough space to develop... Then I went on playing, currently on second year and I met only one race, so upon saving and quitting the game for tonight, I resign so as to see how's the computer doing (yeah I know, call that cheating if you want, I don't care at all) and OMG the korath are like 10 times more points in technology, very close in number of people in empire (I have the lead), and about 5 times(or was it 3 times... don't remember) my economy score. So I'm like OMGWTF, it's insane   !!!! (even though I'm way behind in tech because of the colonize race, and even if my economy is rising)

And true enough I launch TA with cheats just to see all races and as said in the title the korath are at "ultimate"  difficulty ... looking at the others there's 4 intelligent, 3 gifted, and 1 genius .... It's not that much of an issue in itself, I'm just really surprised, because I expect this game will be quite difficult, and I may even lose ... I just hope I'll be able to make the others gang up on the korath which shouldn't be so difficult since they are so evil ... but even then they might be crushed and the korath will only end up with more planets  ....

So to conclude on two things here : is this behavior normal ? back at the time of galciv2 I don't think you could have an ultimate CPU on just "tough" difficulty ???

second thing, if you got any tips... I'm taking lol