To be honest, I'm only putting in the fireplace because it would look stupid without one, as EVERY new home in my area has one. (Most people try to convince me I need one in the office/den and master as well, which I am refusing to do). We will likely seldom use it, though maybe with a gas one I may switch it on some evenings for a bit. We live in California, though we are both transplants here, so we seldom find it cool enough to warrant needing it. Ideally I'd like the fireplace and TV on different walls altogether, but I can't do that without giving up windows, and that isn't an option! Currently our TV is over our fireplace and it doesn't bother me as our mantel is relatively low, and with those new landscape fireplaces it could be lower. For instance, in the second image the TV isn't too high, and I think the fireplace could even be dropped another few inches. I do think I solved my own issue as with the curtains it wouldn't be safe (or look good) to have a corner fireplace. So TV over the fireplace it is :) Also, now that I stare at all these photos some more I realize I like the clean look of not having a table beneath the TV, and if there wasn't a fireplace it looks silly to not have anything under the TV. So the decision is complete! Thanks for your advice, and helping me talk myself into a decision! :)

Personally I'm not a fan of sectionals, but that of course is opinion. If you have room for a sectional you have room for a sofa and two chairs! How often do you anticipate opening and shutting the French doors? To me since the left side only opens 90 degrees it's ok for the right side to as well. Or you could open the right side all the way against the wall and out furniture in front of it. That can work.

Oh you have to turn it into a reading nook! All that beautiful natural lighting and right beside the fireplace for some winter warmth! I lean towards a low wingback chair. Wide enough that you can add an extra pillow and still be able to comfortably tuck your feet up. But low enough that the back of the chair won't block out the window lighting. As for style, I would go a mid-century style. I definitely steer clear of anything too vintage-y, like carved arms and Edwardian details. The cleaner lines of mid-century beside your trim/wainscoting would play nicely. I agree that a hanging plant would be nice, but I'd be careful what kind of plant because it it has flowers your going to get that pollen stuff all over your chair. Though if you're sticking with the pale grey walls, light window coverings and a new lighter rug, I would choose a chair in a medium to dark tone to help anchor the room.

Blocking those vents is not a good idea in the first place, particularly with a wood mantel. It renders the fireplace unusable. Although I am not aware of any particular building code that states it as being a safety issue, I would think any building inspector would deem it so. Regarding ventless logs, they put out a tremendous amount of heat. So not only is that mantel going to get blasted from behind with heat to those vents, it is going to bet hit with heat flowing directly from the fireplace opening. Here's a clearance chart for mantels for a popular ventless log set that our company sells. I suggest you print this out and do some measuring. I don't think your mantel will pass muster. You may need to replace it with a Non-Combustible Steel Mantel: I can help you with the steel mantel and the logs as well as a way to safely cover those vents that is not noticeable. Let me know if you would like me to present some ideas. I'd do it right now, but it will take more time than I have at the moment.