You asked two questions that were really three. First, yes, almost exactly as expected:
1. It plays very similar to vanilla
2. Religion has minor bonuses, on par with some weaker SP
3. Religion is what you want to make out of it - it can have no bearing on winning/losing
4. All of the new civs, units, buildings and tech tree changes are the true value of expansion packs - they did good on those
5. Espionage was left off and will remain off
Second, I found that my Emperor game was easier than other Emperor games I had. I had no early UU and just went with your basic Swords/Catapults and not only did they remain strong longer, but they went up against weaker units and cities. That's what you would expect at Prince/King.
Third, that doesn't make it a sandbox where one doesn't play to win but to simply build. I cannot fathom that but no, the game still have the same victory conditions (diplomacy changed a bit) and the AI does try to beat you, to some extent, as they should. But I guess I have to go back up to Immortal and even Deity to have some good competition, or change some setup settings, I don't know.