Remove the 'vanity'. Make-up/hair in a moist bathroom is counter indicated. You could add a tall linen closet there. The size of the wall your sinks--just choose mathcing mirrors that will share the wall. If you want larger mirrors--go with a light bar over head. Otherwise two sconces one on either side are popular.

Are you gutting the bathroom to the studs or just replacing cabinets with same footprint?

There's currently an angle in the left most wall - we'll remove that to accommodate the drawer base but leave the rest as is.

Are you remodeling the entire bathroom or just looking at doing the mirrors? Below are some ideas for what you might be able to do. You could do two separate mirrors and a storage compartment in the middle?

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First, remove the light fixtures and make sure the wholes are actually centered to the mirror sometimes they didnt do that when they knew they were mounting these style vanity lights. that is going to help you choose the proper mounting plate.

then get 3 light fixtures you like, consider framing in the mirrors that will help update it. have the lights globes hang down. I would get a 4 light and 2 3light fixtures.