Never mind! I figured it out, I had to make nice tight ‘single convex hulls’ for the fingers so the constraints would be based on those and not interfere with each other! (in the Physics Asset edit window, select finger bones, in the ‘Tools’ panel, ‘Body Creation’ Drop down choose ‘Single convex Hull’ and click ‘Add Bodies’, it will create collision and constraints then in the Details panel, you just select limited (or locked) for Angular Limit, locking the Twist and appropriate angle for fingers and thumb! and increase the Linear and Angular Damping to a high number like 5000. I like to turn ‘parent dominates’ on (checked after selecting a constraint) so the finger can be moved without changing your arm or hand pose!