There are too many variables for a definitive determination of blade angle: face contour, beard texture and growth pattern, razor balance, blade keeness, etc., etc., etc. So, a general discussion of blade angle is useful as a starting point, but you're going to have to feel your way to determine what works best on your face with your tools.

This, in part, is why there is a learning curve required for straight shaving. You've got to figure out what works best for you. This is also why some folks may like Dovo vs. TI (or any other brand) and vice-versa.

BTW, this is also why it's fun!