Personally I avoid TV over fireplace at all costs since no matter how low the TV is hung it won't be at eye level at a seated position, which is really the most comfortable height for TV viewing. But if there is no other options consider a more horizontal fireplace so the TV could be as low as possible.

I agree with Dytecture. The TV over the fireplace should be avoided at all costs.

I agree with the above comments. The television should be at eye level when you are seated.

Some people try a tilt-arm mount for over the fireplace. The problem is that the heat from the fireplace can damage the television. In addition, the cables dangle.

I suggest that you get a console/credenza, and build a vertical mounting piece on top, perhaps an adjustable one. Put the cables and accessories in the furniture.