Fireplace size help – fill the wall or leave space?

I’m trying to choose an electric fireplace for this wall and would love some advice. The plan is to place it between the two windows and mount the TV above it. My style is ‘organic transitional’ and trying to make it more cozy 🙂

I’m deciding between 2 options (in pics):

• One with a wood mantel that’s wider and would leave only about 1 inch of space between the mantel and each window.

• A white fireplace that’s a bit narrower and would leave a few more inches of space on each side.

Is there a rule of thumb for this? Is it better to fill the wall more for a built-in look, or leave breathing room between the fireplace and the windows?

A couple other notes:

•I’ll be removing the tall floor lamp in the corner.

•The media console will also go once the TV is mounted.

Open to any other layout or styling ideas too if you see something I’m missing. Thanks!