Have somebody hold a flashlight at different levels pointing down at you while you lean into the mirror and imagine that you're trying to get an eyelash out of your eye. If you are working in your own shadow, the lights are too high. This is why sconces, one on either side of the mirror, are better for best lighting/visibility.

I use a combination of overhead and bottom watering. When overhead watering seedlings, I use only a mist bottle with a pump. The medium is moistened before loading into the trays, it sits overnight, checked for even moisture, then gently loaded into the cell trays and sown. After seeding, a light misting is done repeatedly until the soil is less-than saturated. Water is put into the bottom tray, a dome is placed over top, and away they go. The dome is taken off for a while, and put back on throughout the germination time depending on humidity of the air and the moistness of the mix. Some seeds are given heat. If the soil shows too much drying, it is misted. May seem like a lot of maintenance, but it's really not. You do have to be careful with domes, it's just experience which lets you know when to remove it, and when to keep it on. I like the the surface slightly moist, but not overly wet. Too dry, and crusts form. Too wet, and damping off can happen. Bottom watering, with a good medium, is just science. Capillary action and cohesion are the active forces. Water... wicks. The key, as was mentioned above, is a good seed starting medium. If you are having trouble bottom watering, more than likely you are working with a medium that lacks the structure favoring the bottom-watering technique. Btw... especially in times when I did not have the money, nor enough pots, I transplant my plugs into paper Chinese food containers. Being square, they fit very well together into a tight mass on a tray. However, being wax coated, as long as you don't puncture them, they are water tight. If you rub off the wax they disintegrate. The only way to really tell if they need watering is to pick them up and weight them in your hand. That too, as was mentioned above, is just experience. Again, too much water...because they don't have drainage holes, the soil compacts and you lose air pockets. Too little water, well, that's obvious.

The diagram Sammy posted is a good guide for the height. You could wire for your lights even before you decide which mirror(s) to buy. We did a 6” backsplash and started our beveled, unframed mirrors immediately on top of the splash rather than leaving a space there because the mirrors were filling the whole space wall-to-wall.

This is the OLD vanity & mirrors- I don't have a pic of the new cabinets BUT the new vanity is standard height, (same as in pic) as you can see the mirror is even taller than the vanity- so maybe 48" tall mirror in pic? The new vanity has towers on either end, sinks moved closer together, but lighting still at same height. There will be new, individual mirrors over each sink