In the second photo the electrical cutouts seem to be rather low for lighting. What will this section be?
In the first photo, you will definitely need to change the holes for electrical unless you want to stare at a sconce while brushing your teeth. Try checking out a mirror for above the sink with lighting above. Or smaller sconces on each side of sink with mirror in the middle. Not sure if a sconce on the right will even make sense since sink is not in the middle.

You could put up a big mirror, move the sconces or a line of lights across the top, run the wires behind it rather than reworking everything.

When the electrical was installed all we had was studs. We can move the electrical boxes. In our previous house the lighting was over the mirror and I had a makeup mirror on the counter. The lights over the mirror seemed to cast a shadow down on my face. I read that having lighting at the sides of the mirror made for better lighting. With the set up of the vanities I am a little puzzled. I considered on the vanity with the knee space installing one large mirror, sconces on each side wall then one large light over the mirror.

I think I would get a mirror and some tem lighting, try and move things around, experiment to get it exactly the way you want it.

I would love to see a photo of the finished product! Your cabinetry is gorgeous! I'm debating whether or not to have a makeup counter or linen cabinet just like you have here so if you have any finished photos I would love to see how yours turned out! Beautiful.