Very nice lines. You done a good job hiding the fact that this is CG. The less the player can tell they are surrounded by polygons, the better! Great work.
Or, may be, i have mistake with using smoothing groups, almoust all problem places are on the hard edges, places of contact polygons with different smoothing groups.
You might want to control the way some polygons fold with animation by manually triangulate. It's more an issue on very low poly tho. For the engine, it's the same.
The number of objects may be a bigger problem than texture size or polygon count. Have you read the optimization guide? https://udn.epicgames.com/Three/LevelOptimization.html
that did it! I also found another way to do it in default rendering: Shading --> Polygon Transparency Sorting Thanks guys! This makes it way easier to model.