Dueling focal points in a room can create a challenge when placing furniture! Each item you mention (the fireplace, the TV and the exterior view) has its own importance and therefore we need to highlight each in its own way.
Interior design help online is here! Below is an example of a room I recently designed for a client:
She had room with very similar focal point concerns. In this room, the fireplace took up one entire wall. Because of the size, the fireplace became the number one focal point. I oriented a sectional sofa to face the fireplace. As well, the fireplace was flanked by a pair of comfortable chairs. While the chairs have their backs to the fireplace, they still visually highlight this architectural element.
The TV was the next focal point. While I would prefer to focus more on the lovely outside view, the reality is the most people use their televisions a lot more often than they actually stare out the window. Thus, we needed to be sure the television had good viewing. I placed a corner TV cabinet adjacent to the fireplace for comfortable viewing.
Finally, we addressed the exterior views. Part of our sectional faces the window. For the second window (and the one with the best view) I used a low bench in the window. Not only does the bench draw attention to the view but it gives another spot to sit and enjoy.
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