How many actuators does the F-35 have for each primary control surface?
Just one per control surface.  Though the airplane is unique with using a single Electro-Hydrostatic Actuator (EHA) per control surface as opposed to a centralized hydraulics system.

https://www.f35.com/in-depth/detail/up-in-the-air-understanding-the-f-35-air-vehicle

I don’t know what you mean by active/standby but the surface actuators are commanded by inputs from the flight control computers, which respond as needed to stick and rudder inputs from the pilot to achieve a desired aircraft reaction to a control input.