Pedal spindle to top of saddle height is the most critical sizing dimension, because I don't know anyone with adjustable length legs!
I know that to be able to pedal efficiently, I need a pedal to saddle height of at least 36 1/2", and no matter what frame size I am riding I this dimension is not negotiable downwards. So long as the correct saddle height can be attained then there is a fair bit of leeway in the frame sizing and it comes down to how much seatpost you can tolerate sticking out, how long the reach is along the top tube, and how high you want the head tube to be to achieve a comfortable handlebar height. In the days of steel frames with horizontal top tubes, bike sizing was pretty simple. If you could straddle the frame with your feet on the floor without doing yourself a mischief, then the sizing was in the right ball park to be able to asjust it for comfort.