Both my Hemlock and Summer Season both small have 70mm stems 12degree rise and Nukeproof flat bars cut down to 710.
The Hemlock has no spacers and i'm just under 5'8".
On 685 bars i always seemed to ride with hands on the ends now my hands sit on the grips. Although i occasionaly catch trees now on narrow, techy stuff!
Just changed the forks on the On One and the bar height is 15mm lower on that one and it stills feels good so maybe i can go 0degree on the Hemlock!
Lower = better as far as i'm concerned although you can get to a point where it feels wrong but its worth messing to find out.
More weight on the front = more confidence in corners.
Hope my ramblings help, if not ignore them….