Thanks for the reply. From what I've found, and what I'm doing, is framing and then covering with 5/8 drywall. Then framing the wall in front of it. I don't know if this is necessary for electric direct contact, but it's how you would do a gas insert. Nothing wrong with overbuilding, I suppose.
I went through probably 15 different iterations of fireplace higher or lower, mantel or not, hearth or not. I think this is what I've settled on. Colors may vary:
Some other options I looked into were:
just the fireplace, no surround:
Surrounded by tile, and a stoop.
Traditional look with a stoop, painted white.
Of the different designs I did, I think I like the tile flush with the floor underneath it. The design will stay the same, but I'm not sure for color/materials yet. I'm either going to build it out of all cherry, stained light, all white with a something like poplar, or a combination of white/cherry/tile inserts. Some examples:
I've also killed the idea of the niche above - the wall was too busy.