When you’re using mesh light in Yafaray, their size affects the power and the softness of the shadows. A bigger plane will have more power and softer shadows (it works the same as Area lamps).
You have to checked the normals too, they must point towards the object you want to light, it’s very important. You could enable “Double sided” in the objects panel of the Yafaray GUI if you need to light a large scene.
For the rings of the documentation, they used an hdri texture for the world to make these reflections.
The setup, with materials is saved with the blend file, but I don’t think you can import them between files.
You should have posted that in the support part of the forum, or on the Yafaray website. Maybe a moderator would move this thread in a better place.
So, your second picture is in the right way.You should add another Area lamp (or two) to have some kind of a studio lighting setup: a fill light on the right and a Rim light behind the rings. This method is called Three-Point Lighting.
For the grainy part, you should increase the samples of your Area lamp.
The reflections will give more realism to your rings, so as I told you, you have to use a hdri texture for that.
I strongly recommend you to post this on the Yafaray forum.