My parents house is like that, but there’s a wall with a wide doorway into the area with the vanity, so it’s open but also easy to close off by just putting a curtain rail up. It’s also oriented to the room such that if you only use enough light at the vanity to wash your hands for a midnight potty run, it really isn’t enough to bother someone in the bed if you place the bed sensibly. Getting ready in the morning would be trickier if you needed to do makeup and so on so needed proper lighting, so that’s where a screen or a curtain would come in.

There isn't a rule for light height since wall heights vary, but placement will control the quality of light output. I don't think you mention if these lights are doing all the work for the room or if there are can lights above, or if the vanities are in an alcove vs open in the room. You could lower lights to 80" but you mention you don't want all the extra empty wall space above. I've seen photos where folks take the mirror higher than the lights and lights are mounted through the mirror. Might be easier if you draw it out to see where you want light placement because mirror size will play into it. For example if vanity height is 36" including countertop, will there be a backsplash included to factor in? If there's a 4" backsplash, and you want light at 80" that still leaves you about 40" to work with for mirror placement. Or you could have mirror custom cut to sit at top of backsplash and go to height that works with light placement. The best lighting is closest to your face, so without sconces, you could look to buy a lighted make-up mirror to get the closer up view when you need it.

Ive used these mirrors and the thickness looks great, just be careful if it gets in the way of the sink faucet or its handles. If u can hang the mirror 6-8" above them u will be ok.. :-) Ds

I would have a mirror madeso it goes all the way to the ceiling, mirror is fairly inexpensive and it will make the room look much bigger, perhaps do one with a bevel. Or if youre buying a framed one u probably are needing a size of 72x48 minimum (that will put it almost to the ceiling and look great :-) Ds