Context is key. Do you have any pics you could share?

@millworkman I only have a plan. Would that help?

Only drywall up.

A picture of the wall as is would be helpful if that's what you have. Tape outlines of the mirrors on the wall with painters' tape. What do the light fixtures look like? There are multiple types of vertical fixtures. As far as placement, you want to have the light source at eye level. Based on that rough guideline, where you place the junction box also depends on the fixture.

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