You have to find the best balance of what your knees will handle.
I've got a bad knee and have had to go to 165's to avoid pain and have a semi reasonable cadence.
I'm about 5'11"now, but used to push 6'1" in my "yute".
My results- length vs cadence-
175 60 foot was coming off the pedal in the 12 o'clock position.
170 80
165 85
160 80 Obviously there's a point of going too short. it kind of felt like being on a kids tricycle.
You lose "torque" with a shorter crank, but you make up the difference by spinning lower gears.
I've converted both my bikes to 3X9's and run 12-23 cassettes.
Lots of closely spaced gears to keep my cadence in a narrow range that works best for my knee & emphysema.
As I said, you have to find what works for YOU.