Yes, normal is an easy setting. Tough is where the AI gets the algorithms to recognise and counter what you're doing. Normal it's still drooling and making snarky comments. Gigantic map+ tight clusters (guessing you used that?) is like saying "Hey, I want the AI to be as stupid as possible).
Tough, medium map, scattered stars, everything else up to you. If there are <5 races then they can really shine with things like ship building. This is what I now play for a decently challenging game where the AI doesn't make stupid mistakes (like sending a tiny fleet right into a planet that has Armageddon roughly 5 parsecs behind

)