The 2 electrical spots I see are way too low for sconces so not sure what you want.

You might be ok with three of those, one on either end of mirror and one between zones. Be sure you have enough wattage/lumens though!

I don't see any wiring there for any wall lights. I think three sconces for that area should be sufficient.

Is the light from the sconces necessary? Or are they merely decorative. It seems like a narrow space that could easily get crowded with two sconces. It's hard to judge without the mirror in place.

The electrician is suppose to cut out the hole for the electric bracket.

Scones should be in two's, so do not do three. The sink is not centered in the middle of the vanity, so is your mirror going to be centered on the entire vanity I'm assuming? (it needs to be) Place one scone on either side of the mirror and another different type of light fixture centered above or inside the mirror that compliments.

Here are sconces mounted through the mirrors. You bigger issue is what to do with the poor placement of electrical outlets on that wall.

Get the outlets into the drawers

I too have full wall mirror in new home master. Two sconces one over each sink. Looks great.

Golfgem-do you happen to have picture if your master bath mirror to see?