I get asked about treestand height a lot. I tell everyone to focus on understanding wind and thermals of your location before focusing on a tree height. That nose is more of a concern to me than eye sight. you cannot beat their nose, but you can mitigate them looking around for what smells out of place.
after that, I want cover. what breaks up my outline as much as possible.
Sometimes that is 8' up, sometimes 18'.
I prefer to hunt corridor/edge funnels and that leads me to usually one shooting spot. In my youth I was the guy that wanted to see all the deer and be in that tree that allowed for my visibility. Sound familiar about seeing deer and not having shots?
I forget when it all clicked in my brain but now I typically set up in the funnel with the shooting lane as small as I can get away with. Only hunt when the thermals and wind are appropiate and zero movement in the stand.
back to the how high, most of my stands are 18', but as others have said I range from 6' to 22'. I find the higher stand I use are me needing to be above the line of sight on a ridge and to carry my scent where I want on the given hunt.
and have piles of set ups, don't over hunt a specific stand. dont leave your scent all over the place to smell at night. the more you are there the more they raise an eyebrow. I have several stands that may only get sat in 1-2 hunts the entire year.
man I could talk for hours on this