So common question today for all levels and types of cyclists.
Where should the bars be ? (how high/low)
There is going to be a bunch of personal preference, personal limitations (flexibility), bike type and style of riding that determines how long someone goes but if you go through top riders in any discipline you will rarely see people running bars higher than their seats , or much above the head tube.
This is a great video from Sea Otter on Emily Batty Bike setup . She is a shorter rider (with mad skills) and you can see the adjustments she made on her 29er bike to get low enough.