I'm trying to find lights like these also. Any idea? Or, where to find similar? ty

Sorry. Not really. Fireplaces generally are an energy waster. Unless you get a sealed unit, they pull your heated air and send it up the chimney. Unless you're heating your house via only a wood stove, let's just not bother talking about efficiency. It's a luxury item.
When the Rumsford fireplace was invented, wood was the only source of heat, so extracting every bit of radiant heat they could get from the wood before the smoke went up the chimney was the goal. That's why the opening is wide, and the back of the fireplace has angled sides to reflect the radiant heat out.
If you've eve been by a campfire, or sat in the sun, you know what radiant heat is. It's different from heating the air, which heats your skin. That's called convective heat. Radiant heat comes directly from the source (a fire, or the sun) and hits your skin. The room can be cool, or even cold, yet you can feel warm.

Thanks! I do try to use my heater as little as possible in winter--I much prefer natural wood-burning fireplace heat over the dry heat from a heater. We only have a few very cold months in our region so it's feasible to burn firewood quite often. I'm going to do more research on the Rumsford FP as we hope to build soon because I do at least want the most efficient type of FP. Thanks again!

Did you by any chance get an answer to your floor question. I noticed your porch ideas are similar to mine. I also have a cement covered porch. Looking for ideas. Thank you.

This is slate. Perfectly fine for a concrete base.