In general, how much detail can blind sight interpret? Is it like the Daredevil movie where they can make out an individuals facial details, or more of a "there is a humanoid/quadruped/tentacled horror shape in front of me" type of situation?
The Core Rulebook states that blindsight uses non-visual queues to "operate effectively without vision". The rules are posted verbatim on the PFSRD website
Specifically the rules state:
Blindsight never allows a creature to distinguish color or visual contrast. A creature cannot read with blindsight.
While that prohibits some specific cases, my advice would be to look at pictures of sonograms to get an idea of what level of detail is reasonable. I would think that the movie Daredevil is a little too accurate compared to what the rules allow. I imagine a character would need to rely on scent, the vibration of footsteps or the sound of breathing to identify an individual. They could certainly tell the difference between species, but may have trouble telling the difference between two humans of similar build.
It seems like the rules imply that you should select one source for the blindsight (hearing, smell, vibrations, etc) and that defines the scope of what is possible. A dragon would classically use scent for this, while underwater creatures typically rely on hearing. Some creatures will specifically call this out in their bestiary description, such as Tikoloshe.