In our last house the powder room had about the same sqare feet as yours does, just different dimensions. We had three halogen lights above the mirror and that was plenty of light for everyday use. I don't remember the actual bulb we used as we haven't lived there for almost a year. Just look for sconces that allow a brighter bulb or that use two bulbs in each sconce. I would use the lumen formula davidtay posted above. That will help you decide if the sconces you like will be bright enough. We did have a bathroom fan with a light installed above the toilet. That helped for when I wanted to clean the bathroom, or needed a brighter light for removing slivers, etc. as the bathroom was where we kept our first aid kit, but we could have gotten along fine without it as the light from the vanity fixture was enough for the room.

Because of the lighted niches, I recommend step lighting.

The recessed lights are fine. They are for general lighting. The sconces are the more specific task lighting and will eliminate any shadowing. That’s quite a lot of light, actually. You may want to tweak the wattage of the bulbs later, depending on how it feels after you get it all together. I would also put a dimmer on one or both light switches for late night visits. Tip: address appliance outlets in the vanity while you can - if you haven’t already. If you’re right handed, having the cord strung across the sink is a pain. I had an outlet installed down the right side of the vanity and have my hair dryer on a hook there. You may have a better solution for storage inside, but either way it’s a good time to take care of it.

Well, I am trying to make similar decisions on this myself. I too had come across that it is better to have sink lighting from the side rather than above but have found the layout to be challenging and busy. So, I checked houses for sale with 2500 - 3500 square feet and none of them had side sconces around their mirrors. And only one or two had frames around their bathroom mirrors. Most of them had one large mirror across the sink area with lights over it. A bathroom can be a busy area, so from a minimalist standpoint, no frame. Now a mirror in the Livingroom really needs a frame.