You should be more specific.
If you're asking about this, you probably don't have the required knowledge to make a photorealistic 3d scene and even if you do, you shouldn't. Even AAA games uses enviroments much less photorealistic than they could because of performance. Only If you learn about sculpt and retopo, uv mapping, (good) normal map baking, pbr materials, texturing and lighing a scene properly you'll be able to make a photorealistic scene. About Godot itself, the version 3 have some greate improvements in the rendering engine but it's not so great as other engines (ie Unreal Engine 4). Since i'm assuming you won't do AAA games, even the 2.1.4 version should be enough. Try to learn about all the things necessary to make a great real-time scene and by then Godot 3 will finally be released.