EK3_SRC selection from GPS/OpticalFlow etc

I’m currently involving configure EK3_SRC by RC controller.

And I have noticed that there are two ways:

a) RCx_OPTION = 90 (EKF Pos Source) low is GPS, middle is OpticalFlow, high is unused Optical Flow Sensor Testing and Setup
b) ahrs-source.lua script in GPS / Non-GPS Transitions

I just wanna know where to put lua script, and if I have both configured EK3_SRC1_ EK3_SRC2_ and copied script to sd card, which is active?