Lighting on the side of the face is often a better choice, if you're able. It cast less shadows; easier to put makeup on by. If you put a 2 light fixture above each mirror it probably would be enough, depending on the wattage it can take. I have a sconce on either side of my 21x33 oval mirror, a bit smaller than yours. It is enough lighting. I use 100 watt bulbs in them and I can dim them. My over all size of my bathroom is 6.5x9.5 and lots of light colors & reflective tile surfaces. These 2 lights are all I use for lighting. If I had darker materials in there I might need more lighting than this. I face mine up so I don't have to look at the bulb. I think the 2 vs 3 would be a personal style issue. What looks better. I think either would work. You could do a search on Houzz and look at all kinds of sconce pictures.

I think picking a finish is dependent on your taste and the style you're going for in the room. I picked a satin brass for my bath fixtures because I wanted some warmth mixed in with the distressed/satin nickel plumbing fixtures I'll have. Obviously, I'm not someone who matches finishes. Here are some porcelain ones that are adorable for a vintage bathroom, if that's the direction you're heading. Glass shades, too! Important for cleaning toothpaste splatter. And, up to 100 watts bulbs. That's something I looked for, as well. I needed adequate light in my dark bathroom. Here is a link that might be useful: Bellacor-and they're have discounts avail

Although you see scofflaws violate this a lot, lighting over a tub must be wet area rated and be 96” above the rim, minimum. That rule is in effect to keep you from slipping and grabbing that light, and then electrocuting yourself. If you want a pendant there, make it one that uses candles, not electricity.

It sounds like you might be putting in lights kind of like these (with a long, tall and totally shaded style), but correct me if I'm wrong: In which case, those will be OK to use even if they go above and below their junction box. Still mount them at eye level as you mentioned above, but it's OK that they go above and below it a bit. Let me know if you have any other questions!