Visually speaking and also gameplay wise, games I like tend to look and play like older TB Microprose and spiritual successors, as in MOO 0/1/2, BOF, GC, fans games(BOF2, Star Trek, there is also a German one I forget the name, but started too as a Stratrek BoF clone etc).

So I'm deffinitely gonna try Endless Space too(even though its RT or semiRT). I don't like the Randomness factor people mention in forums, but I'll reserve judgement for, after playing. Seems to have a great UI if anything. Ofcourse gameplay is key as I'm not playing the interface, but merely using it to play and possibly enjoy the game.

It also seems to flow naturally, which is always important in such games. Maybe except combat, that looked a bit forced at a YT video I watched the other day. But good innovation the levels of combat(starting from very far and up to close range), I like innovations, sometimes even if they're not executed that well. At least they tried their best and looks they supported it a lot post release. Companies should do that. Its part of Gamers biil of rights.

I'm quite intrigued by this game myself, though reading about the AI getting a lot of bonuses even at the lower difficulty levels, weird AI decisions and being overwhelmed by large numbers of AI fleets give me the impression that the singleplayer experience is not very good. I honestly hope this would change because everything else about the game seems pretty good.

You have to research tech for diplomacy (also there is a faction that cannot have any diplomacy with anyone) and once you get a peace pact you establish trade with automatically with any system of the AI you discovered. If you want to play a trade empire you want to discover as many possible planets before doing peace treaty (as you are locked out of their space then) or do open borders treaty afterwards. 

You customize ships in fleet screen, but you need to unlock better tech first. You can unlock both new ship hulls and better weapons, armors and additional stuff like engines, siege weaponry and both fighter and bomber tech. 

What do you mean faction have no flexibility at start? 

Smaller maps are tougher games, yes. Play them if you want a bigger challenge. Tech tree is decent, at least the Gold version has a decent one. 

It does not have randomness Sword of the Stars has but it is good enough. Each faction has unique things on tech tree and some of them don't get access to bigger things normal to other faction (one faction cannot do any trade or diplomacy, another does not use food,..)

Morale tech is mostly on the left side of the tech tree. 

Thanks for the advice.

I'm used to playing Galactic civilizations. When you pick a race you have a choice of abilities and political parties. There are other things that are minor.