While the plan you've provided isn't great....if the room is 15,1', then likely you could do facing sofas. Put a krypton/perennial type white fabric on them. Formal does not have to mean too precious to sit upon. Do you have a budget in mind?

The room is not that long and narrow. I misunderstood your plan at first, so the entry is not included here. I didn't have the measurements for it anyway, and it's not really part of the living area. Here's a to-scale drawing with a guess at the locations of window and door.

This is probably your best arrangement with two sofas, assuming the fireplace is centered.

you could have the two sofas facing,but it looks to me like they can NOT be perfectly centered on the fireplace. You have to decide how important that symmetry is for you. And of course,the exact measurement of that fireplace wall is critical to knowing how asymmetrical it would be. (there are a few tricks to make it appear closer to centered)

Further,the access to the Patio is a bit better with the Grover arrangement.

My best advice it to buy nothing until you can get into the empty space,armed with some blue painter tape to figure out a perfect plan. Also,how high is the ceiling?

I do not believe you will want two sofas facing each other. It will look like this:

You can tell how long the sofas are and their placement by counting the squares. One square = one foot.

Grover, in OP's sketch, the window and door does not align, nor is the fireplace centered on wall. Of course that doesn't mean that is how it is IRL but I just don't think this dilemma is at such an exact stage of specificity. Of course,my view is tainted by living in a 1920's house where nothing aligns with such symmetry....not even the fireplace is centered on the wall.

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