I would suggest you consult photos on Houzz...type in fireplace walls...there are so many ideas that look ...important but not imposing...minimal but not boring...simple but not plain....sounds like you would know it if you saw it ....and you know best the overall look you are seeking in this new build

You are on the right path of masking the fireplace on a small scale. If you go with a 60" mantel how much room will there be between the mantle and the TV wall? You definitely want the mantel not to come close to that wall. Another consideration would be furniture on the TV wall. If the mantle bulges out , it will definitely limit the scale of the furniture you plan for the TV wall.

The Fireplace vs TV conundrum is a tough one. In the end it always comes down to deciding which will be the focal point of the room. If you plan to have the sofa/chairs facing the TV wall then perhaps try and make the fireplace less conspicuous.

It is unlikely to be "imposing," given how much stuff usually ends up on a TV wall, unless you were to face it with black stone. Go light, and I think it could be fine framed small or covered to the ceiling.

I think I would skip the mantle and just add molding, continuing along if you can on adjacent wall so there is continuity. You could add stone around the fireplace and add sconces above is another idea. Other option is to add stone just on the fireplace wall right up to the ceiling.

This is all very helpful. Thank you for your input!

I would suggest you clad the FP wall from floor to ceiling in some type of matte finished material and forego the mantle. A modern look might be a nice change.

Mantles then just become a place for stuff. On corner fireplaces, I don't like the fact it extends over the adjacent wall.

Luckily yours is not in a true corner. I know corner FP are a style challenge. I would agree with BeverlyFla & clad it in a tile or stone surface all the way up & go w/o a mantle. Positioning the TV on a low credenza to the right of the FP is best.

This is so helpful and right along the lines of the style and look I was thinking. Many thanks!

What did you end up doing? I have a very similar corner fireplace and I am debating how to do the mantel too!